diff --git a/base/ascii.jl b/base/ascii.jl
deleted file mode 100644
index bb5dd899d52a1..0000000000000
--- a/base/ascii.jl
+++ /dev/null
@@ -1,7 +0,0 @@
-# This file is a part of Julia. License is MIT: http://julialang.org/license
-
-ascii(x) = ascii(convert(String, x))
-ascii(p::Ptr{UInt8}) = ascii(bytestring(p))
-ascii(p::Ptr{UInt8}, len::Integer) = ascii(bytestring(p, len))
-ascii(s::String) = byte_string_classify(s.data) == 1 ? s :
-    throw(ArgumentError("invalid ASCII sequence"))
diff --git a/base/deprecated.jl b/base/deprecated.jl
index 07d4944005fb1..348cce6cdfd27 100644
--- a/base/deprecated.jl
+++ b/base/deprecated.jl
@@ -1155,6 +1155,10 @@ end
 @deprecate_binding UTF8String String
 @deprecate_binding ByteString String
 
+@deprecate ascii(p::Ptr{UInt8}, len::Integer) ascii(bytestring(p, len))
+@deprecate ascii(p::Ptr{UInt8}) ascii(bytestring(p))
+@deprecate ascii(x) ascii(string(x))
+
 @deprecate ==(x::Char, y::Integer) UInt32(x) == y
 @deprecate ==(x::Integer, y::Char) x == UInt32(y)
 @deprecate isless(x::Char, y::Integer) UInt32(x) < y
diff --git a/base/docs/helpdb/Base.jl b/base/docs/helpdb/Base.jl
index 5252a07cc526d..480d57f73e2c5 100644
--- a/base/docs/helpdb/Base.jl
+++ b/base/docs/helpdb/Base.jl
@@ -8719,28 +8719,13 @@ alias the input `x` to modify it in-place.
 filt!
 
 """
-    ascii(::Array{UInt8,1})
+    ascii(s::AbstractString)
 
-Create an ASCII string from a byte array.
-"""
-ascii(::Vector{UInt8})
-
-"""
-    ascii(s)
-
-Convert a string to a contiguous ASCII string (all characters must be valid ASCII characters).
+Convert a string to `String` type and check that it contains only ASCII data, otherwise
+throwing an `ArugmentError` indicating the position of the first non-ASCII byte.
 """
 ascii(s)
 
-"""
-    ascii(::Ptr{UInt8}, [length])
-
-Create an ASCII string from the address of a C (0-terminated) string encoded in ASCII. A
-copy is made; the ptr can be safely freed. If `length` is specified, the string does not
-have to be 0-terminated.
-"""
-ascii(::Ptr{UInt8},?)
-
 """
     maxabs(itr)
 
diff --git a/base/printf.jl b/base/printf.jl
index c2882d65452c1..448b845fc869d 100644
--- a/base/printf.jl
+++ b/base/printf.jl
@@ -98,7 +98,7 @@ function parse1(s::AbstractString, k::Integer)
     while c in "#0- + '"
         c, k = next_or_die(s,k)
     end
-    flags = ascii(s[j:k-2])
+    flags = String(s[j:k-2])
     # parse width
     while '0' <= c <= '9'
         width = 10*width + c-'0'
diff --git a/base/socket.jl b/base/socket.jl
index 9f8bc27c3b6a6..2c5ee4e3e81af 100644
--- a/base/socket.jl
+++ b/base/socket.jl
@@ -586,6 +586,7 @@ function uv_getaddrinfocb(req::Ptr{Void}, status::Cint, addrinfo::Ptr{Void})
 end
 
 function getaddrinfo(cb::Function, host::String)
+    isascii(host) || error("non-ASCII hostname: $host")
     callback_dict[cb] = cb
     status = ccall(:jl_getaddrinfo, Int32, (Ptr{Void}, Cstring, Ptr{UInt8}, Any, Ptr{Void}),
                    eventloop(), host, C_NULL, cb, uv_jl_getaddrinfocb::Ptr{Void})
@@ -598,10 +599,9 @@ function getaddrinfo(cb::Function, host::String)
     end
     return nothing
 end
-getaddrinfo(cb::Function, host::AbstractString) = getaddrinfo(cb,ascii(host))
+getaddrinfo(cb::Function, host::AbstractString) = getaddrinfo(cb, String(host))
 
 function getaddrinfo(host::String)
-    isascii(host) || error("non-ASCII hostname: $host")
     c = Condition()
     getaddrinfo(host) do IP
         notify(c,IP)
diff --git a/base/strings/util.jl b/base/strings/util.jl
index 726339d529955..38c2cd9e5f82b 100644
--- a/base/strings/util.jl
+++ b/base/strings/util.jl
@@ -243,3 +243,13 @@ function bytes2hex(a::AbstractArray{UInt8})
     end
     return String(b)
 end
+
+# check for pure ASCII-ness
+
+function ascii(s::String)
+    for (i, b) in enumerate(s.data)
+        b < 0x80 || throw(ArgumentError("invalid ASCII at index $i in $(repr(s))"))
+    end
+    return s
+end
+ascii(x::AbstractString) = ascii(convert(String, x))
diff --git a/base/sysimg.jl b/base/sysimg.jl
index aed8231efd4c9..8a9e4d264d590 100644
--- a/base/sysimg.jl
+++ b/base/sysimg.jl
@@ -125,7 +125,6 @@ include("iobuffer.jl")
 
 # strings & printing
 include("char.jl")
-include("ascii.jl")
 include("string.jl")
 include("unicode.jl")
 include("parse.jl")
diff --git a/doc/stdlib/strings.rst b/doc/stdlib/strings.rst
index f05af60aba917..1e38401839a13 100644
--- a/doc/stdlib/strings.rst
+++ b/doc/stdlib/strings.rst
@@ -62,24 +62,12 @@
 
    Convert a string to a contiguous byte array representation appropriate for passing it to C functions. The string will be encoded as either ASCII or UTF-8.
 
-.. function:: ascii(::Array{UInt8,1})
-
-   .. Docstring generated from Julia source
-
-   Create an ASCII string from a byte array.
-
-.. function:: ascii(s)
+.. function:: ascii(s::AbstractString)
 
    .. Docstring generated from Julia source
 
    Convert a string to a contiguous ASCII string (all characters must be valid ASCII characters).
 
-.. function:: ascii(::Ptr{UInt8}, [length])
-
-   .. Docstring generated from Julia source
-
-   Create an ASCII string from the address of a C (0-terminated) string encoded in ASCII. A copy is made; the ptr can be safely freed. If ``length`` is specified, the string does not have to be 0-terminated.
-
 .. function:: utf8(::Array{UInt8,1})
 
    .. Docstring generated from Julia source
diff --git a/examples/clustermanager/simple/UnixDomainCM.jl b/examples/clustermanager/simple/UnixDomainCM.jl
index a67f68692f323..8adc39cdd5555 100644
--- a/examples/clustermanager/simple/UnixDomainCM.jl
+++ b/examples/clustermanager/simple/UnixDomainCM.jl
@@ -44,7 +44,7 @@ function connect(manager::UnixDomainCM, pid::Int, config::WorkerConfig)
             if isa(address, Tuple)
                 sock = connect(address...)
             else
-                sock = connect(ascii(address))
+                sock = connect(address)
             end
             return (sock, sock)
         catch e
@@ -62,7 +62,7 @@ end
 function start_worker(sockname, cookie)
     Base.init_worker(cookie, UnixDomainCM(0))
 
-    srvr = listen(ascii(sockname))
+    srvr = listen(sockname)
     while true
         sock = accept(srvr)
         Base.process_messages(sock, sock)
diff --git a/examples/lru_test.jl b/examples/lru_test.jl
index cadf5212d3d67..57fca9e097980 100644
--- a/examples/lru_test.jl
+++ b/examples/lru_test.jl
@@ -5,7 +5,7 @@ using LRUExample
 TestLRU = LRUExample.UnboundedLRU{String, String}()
 TestBLRU = LRUExample.BoundedLRU{String, String}(1000)
 
-get_str(i) = ascii(vcat(map(x->[x>>4; x&0x0F], reinterpret(UInt8, [Int32(i)]))...))
+get_str(i) = String(vcat(map(x->[x>>4; x&0x0F], reinterpret(UInt8, [Int32(i)]))...))
 
 isbounded{L<:LRUExample.LRU}(::Type{L}) = any(map(n->n==:maxsize, fieldnames(L)))
 isbounded{L<:LRUExample.LRU}(l::L) = isbounded(L)
diff --git a/test/strings/basic.jl b/test/strings/basic.jl
index 99cab256668ef..a1d295c03393a 100644
--- a/test/strings/basic.jl
+++ b/test/strings/basic.jl
@@ -216,17 +216,13 @@ end
 # issue #11142
 s = "abcdefghij"
 sp = pointer(s)
-@test ascii(sp) == s
-@test ascii(sp,5) == "abcde"
-@test typeof(ascii(sp)) == String
+@test utf8(sp) == s
+@test utf8(sp,5) == "abcde"
 @test typeof(utf8(sp)) == String
 s = "abcde\uff\u2000\U1f596"
 sp = pointer(s)
 @test utf8(sp) == s
 @test utf8(sp,5) == "abcde"
-@test_throws ArgumentError ascii(sp)
-@test ascii(sp, 5) == "abcde"
-@test_throws ArgumentError ascii(sp, 6)
 @test typeof(utf8(sp)) == String
 
 @test get(tryparse(BigInt, "1234567890")) == BigInt(1234567890)
@@ -494,7 +490,13 @@ foobaz(ch) = reinterpret(Char, typemax(UInt32))
 # `bytestring`, `ascii` and `utf8`
 @test_throws ArgumentError bytestring(Ptr{UInt8}(0))
 @test_throws ArgumentError bytestring(Ptr{UInt8}(0), 10)
-@test_throws ArgumentError ascii(Ptr{UInt8}(0))
-@test_throws ArgumentError ascii(Ptr{UInt8}(0), 10)
 @test_throws ArgumentError utf8(Ptr{UInt8}(0))
 @test_throws ArgumentError utf8(Ptr{UInt8}(0), 10)
+
+# ascii works on ASCII strings and fails on non-ASCII strings
+@test ascii("Hello, world") == "Hello, world"
+@test typeof(ascii("Hello, world")) == String
+@test ascii(utf32("Hello, world")) == "Hello, world"
+@test typeof(ascii(utf32("Hello, world"))) == String
+@test_throws ArgumentError ascii("Hello, ∀")
+@test_throws ArgumentError ascii(utf32("Hello, ∀"))