diff --git a/NEWS.md b/NEWS.md
index e96eef4fc1e54..683b3c6d4fa58 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -367,6 +367,13 @@ Deprecated or removed
 
   * Instead of `linrange`, use `linspace` ([#9666]).
 
+  * The functions `is_valid_char`, `is_valid_ascii`, `is_valid_utf8`, `is_valid_utf16`, and
+    `is_valid_utf32` have been replaced by generic `isvalid` methods.
+    The single argument form `isvalid(value)` can now be used for values of type `Char`, `ASCIIString`,
+    `UTF8String`, `UTF16String` and `UTF32String`.
+    The two argument form `isvalid(type, value)` can be used with the above types, with values
+    of type `Vector{UInt8}`, `Vector{UInt16}`, `Vector{UInt32}`, and `Vector{Char}` ([#11241]).
+
 Julia v0.3.0 Release Notes
 ==========================
 
@@ -1379,6 +1386,7 @@ Too numerous to mention.
 [#9779]: https://github.com/JuliaLang/julia/issues/9779
 [#9862]: https://github.com/JuliaLang/julia/issues/9862
 [#9957]: https://github.com/JuliaLang/julia/issues/9957
+[#10008]: https://github.com/JuliaLang/julia/issues/10008
 [#10024]: https://github.com/JuliaLang/julia/issues/10024
 [#10031]: https://github.com/JuliaLang/julia/issues/10031
 [#10075]: https://github.com/JuliaLang/julia/issues/10075
@@ -1406,5 +1414,9 @@ Too numerous to mention.
 [#10888]: https://github.com/JuliaLang/julia/issues/10888
 [#10893]: https://github.com/JuliaLang/julia/issues/10893
 [#10914]: https://github.com/JuliaLang/julia/issues/10914
+[#10955]: https://github.com/JuliaLang/julia/issues/10955
 [#10994]: https://github.com/JuliaLang/julia/issues/10994
+[#11105]: https://github.com/JuliaLang/julia/issues/11105
 [#11145]: https://github.com/JuliaLang/julia/issues/11145
+[#11171]: https://github.com/JuliaLang/julia/issues/11171
+[#11241]: https://github.com/JuliaLang/julia/issues/11241
diff --git a/base/ascii.jl b/base/ascii.jl
index da70742cc61d6..940f957f8e948 100644
--- a/base/ascii.jl
+++ b/base/ascii.jl
@@ -100,7 +100,7 @@ ascii(x) = convert(ASCIIString, x)
 convert(::Type{ASCIIString}, s::ASCIIString) = s
 convert(::Type{ASCIIString}, s::UTF8String) = ascii(s.data)
 convert(::Type{ASCIIString}, a::Vector{UInt8}) = begin
-    is_valid_ascii(a) || throw(ArgumentError("invalid ASCII sequence"))
+    isvalid(ASCIIString,a) || throw(ArgumentError("invalid ASCII sequence"))
     return ASCIIString(a)
 end
 
diff --git a/base/deprecated.jl b/base/deprecated.jl
index 4d2c645230bb4..c10cbd3185041 100644
--- a/base/deprecated.jl
+++ b/base/deprecated.jl
@@ -443,3 +443,16 @@ export float32_isvalid, float64_isvalid
 @deprecate (&)(x::Char, y::Char)  Char(UInt32(x) & UInt32(y))
 @deprecate (|)(x::Char, y::Char)  Char(UInt32(x) | UInt32(y))
 @deprecate ($)(x::Char, y::Char)  Char(UInt32(x) $ UInt32(y))
+
+# 11241
+
+@deprecate is_valid_char(ch::Char) isvalid(ch)
+@deprecate is_valid_char(ch::Union(Unsigned, Integer)) isvalid(Char, ch)
+@deprecate is_valid_ascii(str::ASCIIString) isvalid(str)
+@deprecate is_valid_ascii(str::Union(AbstractArray{UInt8}, UTF8String)) isvalid(ASCIIString, str)
+@deprecate is_valid_utf8(str::UTF8String) isvalid(str)
+@deprecate is_valid_utf8(str::Union(AbstractArray{UInt8}, ASCIIString)) isvalid(UTF8String, str)
+@deprecate is_valid_utf16(str::UTF16String) isvalid(str)
+@deprecate is_valid_utf16(str::AbstractArray{UInt16}) isvalid(UTF16String, str)
+@deprecate is_valid_utf32(str::UTF32String) isvalid(str)
+@deprecate is_valid_utf32(str::AbstractArray{UInt32}) isvalid(UTF32String, str)
diff --git a/base/exports.jl b/base/exports.jl
index c597161bd1d62..3ebf2be2733d2 100644
--- a/base/exports.jl
+++ b/base/exports.jl
@@ -820,11 +820,6 @@ export
     ind2chr,
     info,
     is_assigned_char,
-    is_valid_ascii,
-    is_valid_char,
-    is_valid_utf8,
-    is_valid_utf16,
-    is_valid_utf32,
     isalnum,
     isalpha,
     isascii,
diff --git a/base/io.jl b/base/io.jl
index c8023d7d77df3..7d0eb16d67c75 100644
--- a/base/io.jl
+++ b/base/io.jl
@@ -246,7 +246,7 @@ end
 
 function readall(s::IO)
     b = readbytes(s)
-    return is_valid_ascii(b) ? ASCIIString(b) : UTF8String(b)
+    return isvalid(ASCIIString, b) ? ASCIIString(b) : UTF8String(b)
 end
 readall(filename::AbstractString) = open(readall, filename)
 
diff --git a/base/string.jl b/base/string.jl
index 8a7e83f4e0cbd..7295a231eea89 100644
--- a/base/string.jl
+++ b/base/string.jl
@@ -968,8 +968,8 @@ byte_string_classify(s::ByteString) = byte_string_classify(s.data)
     # 1: valid ASCII
     # 2: valid UTF-8
 
-is_valid_ascii(s::Union(Array{UInt8,1},ByteString)) = byte_string_classify(s) == 1
-is_valid_utf8(s::Union(Array{UInt8,1},ByteString)) = byte_string_classify(s) != 0
+isvalid(::Type{ASCIIString}, s::Union(Array{UInt8,1},ByteString)) = byte_string_classify(s) == 1
+isvalid(::Type{UTF8String}, s::Union(Array{UInt8,1},ByteString)) = byte_string_classify(s) != 0
 
 ## multiline strings ##
 
diff --git a/base/utf16.jl b/base/utf16.jl
index 2a6ec9b571167..59c1e37cc799a 100644
--- a/base/utf16.jl
+++ b/base/utf16.jl
@@ -95,7 +95,7 @@ sizeof(s::UTF16String) = sizeof(s.data) - sizeof(UInt16)
 unsafe_convert{T<:Union(Int16,UInt16)}(::Type{Ptr{T}}, s::UTF16String) =
     convert(Ptr{T}, pointer(s))
 
-function is_valid_utf16(data::AbstractArray{UInt16})
+function isvalid(::Type{UTF16String}, data::AbstractArray{UInt16})
     i = 1
     n = length(data) # this may include NULL termination; that's okay
     while i < n # check for unpaired surrogates
@@ -110,10 +110,8 @@ function is_valid_utf16(data::AbstractArray{UInt16})
     return i > n || !utf16_is_surrogate(data[i])
 end
 
-is_valid_utf16(s::UTF16String) = is_valid_utf16(s.data)
-
 function convert(::Type{UTF16String}, data::AbstractVector{UInt16})
-    !is_valid_utf16(data) && throw(ArgumentError("invalid UTF16 data"))
+    !isvalid(UTF16String, data) && throw(ArgumentError("invalid UTF16 data"))
     len = length(data)
     d = Array(UInt16, len + 1)
     d[end] = 0 # NULL terminate
@@ -144,7 +142,7 @@ function convert(T::Type{UTF16String}, bytes::AbstractArray{UInt8})
         copy!(d,1, data,1, length(data)) # assume native byte order
     end
     d[end] = 0 # NULL terminate
-    !is_valid_utf16(d) && throw(ArgumentError("invalid UTF16 data"))
+    !isvalid(UTF16String, d) && throw(ArgumentError("invalid UTF16 data"))
     UTF16String(d)
 end
 
diff --git a/base/utf32.jl b/base/utf32.jl
index 5415b222888a7..306abcb24a95d 100644
--- a/base/utf32.jl
+++ b/base/utf32.jl
@@ -92,13 +92,14 @@ function convert(T::Type{UTF32String}, bytes::AbstractArray{UInt8})
     UTF32String(d)
 end
 
-function is_valid_utf32(s::Union(Vector{Char}, Vector{UInt32}))
-    for i=1:length(s)
-        @inbounds if !is_valid_char(reinterpret(UInt32, s[i])) ; return false ; end
+function isvalid(::Type{UTF32String}, str::Union(Vector{Char}, Vector{UInt32}))
+    for i=1:length(str)
+        @inbounds if !isvalid(Char, reinterpret(UInt32, str[i])) ; return false ; end
     end
     return true
 end
-is_valid_utf32(s::UTF32String) = is_valid_utf32(s.data)
+isvalid(str::Vector{Char}) = isvalid(UTF32String, str)
+isvalid{T<:Union(ASCIIString,UTF8String,UTF16String,UTF32String)}(str::T) = isvalid(T, str.data)
 
 utf32(p::Ptr{Char}, len::Integer) = utf32(pointer_to_array(p, len))
 utf32(p::Union(Ptr{UInt32}, Ptr{Int32}), len::Integer) = utf32(convert(Ptr{Char}, p), len)
diff --git a/base/utf8.jl b/base/utf8.jl
index 07859349e1784..f288a1c0fa3dd 100644
--- a/base/utf8.jl
+++ b/base/utf8.jl
@@ -212,7 +212,7 @@ write(io::IO, s::UTF8String) = write(io, s.data)
 utf8(x) = convert(UTF8String, x)
 convert(::Type{UTF8String}, s::UTF8String) = s
 convert(::Type{UTF8String}, s::ASCIIString) = UTF8String(s.data)
-convert(::Type{UTF8String}, a::Array{UInt8,1}) = is_valid_utf8(a) ? UTF8String(a) : throw(ArgumentError("invalid UTF-8 sequence"))
+convert(::Type{UTF8String}, a::Array{UInt8,1}) = isvalid(UTF8String, a) ? UTF8String(a) : throw(ArgumentError("invalid UTF-8 sequence"))
 function convert(::Type{UTF8String}, a::Array{UInt8,1}, invalids_as::AbstractString)
     l = length(a)
     idx = 1
diff --git a/base/utf8proc.jl b/base/utf8proc.jl
index 842a79429f059..fc60350f8545a 100644
--- a/base/utf8proc.jl
+++ b/base/utf8proc.jl
@@ -3,19 +3,21 @@
 # Various Unicode functionality from the utf8proc library
 module UTF8proc
 
-import Base: show, showcompact, ==, hash, string, symbol, isless, length, eltype, start, next, done, convert
+import Base: show, showcompact, ==, hash, string, symbol, isless, length, eltype, start, next, done, convert, isvalid
 
 export isgraphemebreak
 
 # also exported by Base:
-export normalize_string, graphemes, is_valid_char, is_assigned_char, charwidth,
+export normalize_string, graphemes, is_assigned_char, charwidth, isvalid,
    islower, isupper, isalpha, isdigit, isnumber, isalnum,
    iscntrl, ispunct, isspace, isprint, isgraph, isblank
 
 # whether codepoints are valid Unicode scalar values, i.e. 0-0xd7ff, 0xe000-0x10ffff
-is_valid_char(ch::Unsigned) = !Bool((ch-0xd800<0x800)|(ch>0x10ffff))
-is_valid_char(ch::Integer) = is_valid_char(Unsigned(ch))
-is_valid_char(ch::Char) = is_valid_char(UInt32(ch))
+isvalid(::Type{Char}, ch::Unsigned) = !((ch - 0xd800 < 0x800) | (ch > 0x10ffff))
+isvalid(::Type{Char}, ch::Integer) = isvalid(Char, Unsigned(ch))
+isvalid(::Type{Char}, ch::Char) = isvalid(Char, UInt32(ch))
+
+isvalid(ch::Char) = isvalid(Char, ch)
 
 # utf8 category constants
 const UTF8PROC_CATEGORY_CN = 0
diff --git a/doc/manual/strings.rst b/doc/manual/strings.rst
index 15fcfe8859e5b..8969095c609ce 100644
--- a/doc/manual/strings.rst
+++ b/doc/manual/strings.rst
@@ -99,14 +99,14 @@ convert an integer value back to a :obj:`Char` just as easily:
 Not all integer values are valid Unicode code points, but for
 performance, the :func:`Char` conversion does not check that every character
 value is valid. If you want to check that each converted value is a
-valid code point, use the :func:`is_valid_char` function:
+valid code point, use the :func:`isvalid` function:
 
 .. doctest::
 
     julia> Char(0x110000)
     '\U110000'
 
-    julia> is_valid_char(0x110000)
+    julia> isvalid(Char, 0x110000)
     false
 
 As of this writing, the valid Unicode code points are ``U+00`` through
diff --git a/doc/stdlib/strings.rst b/doc/stdlib/strings.rst
index 4a88a4fadbf43..b05d50f3fb72f 100644
--- a/doc/stdlib/strings.rst
+++ b/doc/stdlib/strings.rst
@@ -109,17 +109,19 @@
    even though they may contain more than one codepoint; for example
    a letter combined with an accent mark is a single grapheme.)
 
-.. function:: is_valid_ascii(s) -> Bool
+.. function:: isvalid(value) -> Bool
 
-   Returns true if the argument (``ASCIIString``, ``UTF8String``, or byte vector) is valid ASCII, false otherwise.
+   Returns true if the given value is valid for its type,
+   which currently can be one of ``Char``, ``ASCIIString``, ``UTF8String``, ``UTF16String``, or ``UTF32String``
 
-.. function:: is_valid_utf8(s) -> Bool
+.. function:: isvalid(T, value) -> Bool
 
-   Returns true if the argument (``ASCIIString``, ``UTF8String``, or byte vector) is valid UTF-8, false otherwise.
-
-.. function:: is_valid_char(c) -> Bool
-
-   Returns true if the given char or integer is a valid Unicode code point.
+   Returns true if the given value is valid for that type.
+   Types currently can be ``Char``, ``ASCIIString``, ``UTF8String``, ``UTF16String``, or ``UTF32String``
+   Values for ``Char`` can be of type ``Char`` or ``UInt32``
+   Values for ``ASCIIString`` and ``UTF8String`` can be of that type, or ``Vector{UInt8}``
+   Values for ``UTF16String`` can be ``UTF16String`` or ``Vector{UInt16}``
+   Values for ``UTF32String`` can be ``UTF32String``, ``Vector{Char}`` or ``Vector{UInt32}``
 
 .. function:: is_assigned_char(c) -> Bool
 
@@ -379,10 +381,6 @@
 
    Create a string from the address of a NUL-terminated UTF-16 string. A copy is made; the pointer can be safely freed. If ``length`` is specified, the string does not have to be NUL-terminated.
 
-.. function:: is_valid_utf16(s) -> Bool
-
-   Returns true if the argument (``UTF16String`` or ``UInt16`` array) is valid UTF-16.
-
 .. function:: utf32(s)
 
    Create a UTF-32 string from a byte array, array of ``UInt32``, or
diff --git a/test/strings.jl b/test/strings.jl
index 9e0ae6a0c5135..1f520aa7d4eaf 100644
--- a/test/strings.jl
+++ b/test/strings.jl
@@ -1281,44 +1281,106 @@ end
 @test isxdigit("a") == true
 @test isxdigit("g") == false
 
-@test is_valid_ascii("is_valid_ascii") == true
-@test is_valid_ascii("Σ_not_valid_ascii") == false
-@test is_valid_char('a') == true
-@test is_valid_char('\x00') == true
-@test is_valid_char(0xd800) == false
-
-@test is_valid_utf16(utf16("a")) == true
-@test is_valid_utf16(UInt16[0xd800,0]) == false
-# TODO is_valid_utf8
-
 # Issue #11140
-@test is_valid_utf32(utf32("a")) == true
-@test is_valid_utf32(utf32("\x00")) == true
-@test is_valid_utf32(UInt32[0xd800,0]) == false
+@test isvalid(utf32("a")) == true
+@test isvalid(utf32("\x00")) == true
+@test isvalid(UTF32String, UInt32[0xd800,0]) == false
+
+# Issue #11241
+
+@test isvalid(ASCIIString, "is_valid_ascii") == true
+@test isvalid(ASCIIString, "Σ_not_valid_ascii") == false
+
+# test all edge conditions
+for (val, pass) in (
+        (0, true), (0xd7ff, true),
+        (0xd800, false), (0xdfff, false),
+        (0xe000, true), (0xffff, true),
+        (0x10000, true), (0x10ffff, true),
+        (0x110000, false)
+    )
+    @test isvalid(Char, val) == pass
+end
+for (val, pass) in (
+        (b"\x00", true),
+        (b"\x7f", true),
+        (b"\x80", false),
+        (b"\xbf", false),
+        (b"\xc0", false),
+        (b"\xff", false),
+        (b"\xc0\x80", false),
+        (b"\xc1\x80", false),
+        (b"\xc2\x80", true),
+        (b"\xc2\xc0", false),
+        (b"\xed\x9f\xbf", true),
+        (b"\xed\xa0\x80", false),
+        (b"\xed\xbf\xbf", false),
+        (b"\xee\x80\x80", true),
+        (b"\xef\xbf\xbf", true),
+        (b"\xf0\x90\x80\x80", true),
+        (b"\xf4\x8f\xbf\xbf", true),
+        (b"\xf4\x90\x80\x80", false),
+        (b"\xf5\x80\x80\x80", false),
+        (b"\ud800\udc00", false),
+        (b"\udbff\udfff", false),
+        (b"\ud800\u0100", false),
+        (b"\udc00\u0100", false),
+        (b"\udc00\ud800", false)
+        )
+    @test isvalid(UTF8String, val) == pass
+end
+for (val, pass) in (
+        (UInt16[0x0000], true),
+        (UInt16[0xd7ff,0], true),
+        (UInt16[0xd800,0], false),
+        (UInt16[0xdfff,0], false),
+        (UInt16[0xe000,0], true),
+        (UInt16[0xffff,0], true),
+        (UInt16[0xd800,0xdc00,0], true),
+        (UInt16[0xdbff,0xdfff,0], true),
+        (UInt16[0xd800,0x0100,0], false),
+        (UInt16[0xdc00,0x0100,0], false),
+        (UInt16[0xdc00,0xd800,0], false)
+        )
+    @test isvalid(UTF16String, val) == pass
+end
+for (val, pass) in (
+        (UInt32[0x0000], true),
+        (UInt32[0xd7ff,0], true),
+        (UInt32[0xd800,0], false),
+        (UInt32[0xdfff,0], false),
+        (UInt32[0xe000,0], true),
+        (UInt32[0xffff,0], true),
+        (UInt32[0x100000,0], true),
+        (UInt32[0x10ffff,0], true),
+        (UInt32[0x110000,0], false),
+        )
+    @test isvalid(UTF32String, val) == pass
+end
 
 # Issue #11203
-@test is_valid_ascii(UInt8[]) == true
-@test is_valid_utf8(UInt8[]) == true
-@test is_valid_utf16(UInt16[]) == true
-@test is_valid_utf32(UInt32[]) == true
+@test isvalid(ASCIIString,UInt8[]) == true
+@test isvalid(UTF8String, UInt8[]) == true
+@test isvalid(UTF16String,UInt16[]) == true
+@test isvalid(UTF32String,UInt32[]) == true
 
 # Check UTF-8 characters
 # Check ASCII range (true),
 # then single continuation bytes and lead bytes with no following continuation bytes (false)
 for (rng,flg) in ((0:0x7f, true), (0x80:0xff, false))
     for byt in rng
-        @test is_valid_utf8(UInt8[byt]) == flg
+        @test isvalid(UTF8String, UInt8[byt]) == flg
     end
 end
 # Check overlong lead bytes for 2-character sequences (false)
 for byt = 0xc0:0xc1
-    @test is_valid_utf8(UInt8[byt,0x80]) == false
+    @test isvalid(UTF8String, UInt8[byt,0x80]) == false
 end
 # Check valid lead-in to two-byte sequences (true)
 for byt = 0xc2:0xdf
     for (rng,flg) in ((0x00:0x7f, false), (0x80:0xbf, true), (0xc0:0xff, false))
         for cont in rng
-            @test is_valid_utf8(UInt8[byt, cont]) == flg
+            @test isvalid(UTF8String, UInt8[byt, cont]) == flg
         end
     end
 end
@@ -1326,11 +1388,11 @@ end
 for r1 in (0xe0:0xec, 0xee:0xef)
     for byt = r1
         # Check for short sequence
-        @test is_valid_utf8(UInt8[byt]) == false
+        @test isvalid(UTF8String, UInt8[byt]) == false
         for (rng,flg) in ((0x00:0x7f, false), (0x80:0xbf, true), (0xc0:0xff, false))
             for cont in rng
-                @test is_valid_utf8(UInt8[byt, cont]) == false
-                @test is_valid_utf8(UInt8[byt, cont, 0x80]) == flg
+                @test isvalid(UTF8String, UInt8[byt, cont]) == false
+                @test isvalid(UTF8String, UInt8[byt, cont, 0x80]) == flg
             end
         end
     end
@@ -1339,8 +1401,8 @@ end
 # Check for short sequence, or start of surrogate pair
 for (rng,flg) in ((0x00:0x7f, false), (0x80:0x9f, true), (0xa0:0xff, false))
     for cont in rng
-        @test is_valid_utf8(UInt8[0xed, cont]) == false
-        @test is_valid_utf8(UInt8[0xed, cont, 0x80]) == flg
+        @test isvalid(UTF8String, UInt8[0xed, cont]) == false
+        @test isvalid(UTF8String, UInt8[0xed, cont, 0x80]) == flg
     end
 end
 # Check valid four-byte sequences
@@ -1354,22 +1416,22 @@ for byt = 0xf0:0xf4
     end
     for (rng,flg) in r0
         for cont in rng
-            @test is_valid_utf8(UInt8[byt, cont]) == false
-            @test is_valid_utf8(UInt8[byt, cont, 0x80]) == false
-            @test is_valid_utf8(UInt8[byt, cont, 0x80, 0x80]) == flg
+            @test isvalid(UTF8String, UInt8[byt, cont]) == false
+            @test isvalid(UTF8String, UInt8[byt, cont, 0x80]) == false
+            @test isvalid(UTF8String, UInt8[byt, cont, 0x80, 0x80]) == flg
         end
     end
 end
 # Check five-byte sequences, should be invalid
 for byt = 0xf8:0xfb
-    @test is_valid_utf8(UInt8[byt, 0x80, 0x80, 0x80, 0x80]) == false
+    @test isvalid(UTF8String, UInt8[byt, 0x80, 0x80, 0x80, 0x80]) == false
 end
 # Check six-byte sequences, should be invalid
 for byt = 0xfc:0xfd
-    @test is_valid_utf8(UInt8[byt, 0x80, 0x80, 0x80, 0x80, 0x80]) == false
+    @test isvalid(UTF8String, UInt8[byt, 0x80, 0x80, 0x80, 0x80, 0x80]) == false
 end
 # Check seven-byte sequences, should be invalid
-@test is_valid_utf8(UInt8[0xfe, 0x80, 0x80, 0x80, 0x80, 0x80]) == false
+@test isvalid(UTF8String, UInt8[0xfe, 0x80, 0x80, 0x80, 0x80, 0x80]) == false
 
 # This caused JuliaLang/JSON.jl#82
 @test first('\x00':'\x7f') === '\x00'