diff --git a/doc/site/modules/core/string.markdown b/doc/site/modules/core/string.markdown
index 8d28cb4e..b9b459e6 100644
--- a/doc/site/modules/core/string.markdown
+++ b/doc/site/modules/core/string.markdown
@@ -129,28 +129,12 @@ negative to count backwards from the end of the string.
 It is a runtime error if `search` is not a string or `start` is not an integer
 index within the string's byte length.
 
-### **split**(separator)
-
-Returns a list of one or more strings separated by `separator`.
-
-    :::wren
-    var string = "abc abc abc"
-    System.print(string.split(" ")) //> [abc, abc, abc]
-
-It is a runtime error if `separator` is not a string or is an empty string.
-
-### **replace**(old, swap)
-
-Returns a new string with all occurences of `old` replaced with `swap`.
-
-    :::wren
-    var string = "abc abc abc"
-    System.print(string.replace(" ", "")) //> abcabcabc
-
 ### **iterate**(iterator), **iteratorValue**(iterator)
 
-Implements the [iterator protocol](../../control-flow.html#the-iterator-protocol)
-for iterating over the *code points* in the string:
+Implements the [iterator protocol][] for iterating over the *code points* in the
+string:
+
+[iterator protocol]: ../../control-flow.html#the-iterator-protocol
 
     :::wren
     var codePoints = []
@@ -163,12 +147,74 @@ for iterating over the *code points* in the string:
 If the string contains any bytes that are not valid UTF-8, this iterates over
 those too, one byte at a time.
 
+### **replace**(old, swap)
+
+Returns a new string with all occurrences of `old` replaced with `swap`.
+
+    :::wren
+    var string = "abc abc abc"
+    System.print(string.replace(" ", "")) //> abcabcabc
+
+### **split**(separator)
+
+Returns a list of one or more strings separated by `separator`.
+
+    :::wren
+    var string = "abc abc abc"
+    System.print(string.split(" ")) //> [abc, abc, abc]
+
+It is a runtime error if `separator` is not a string or is an empty string.
+
 ### **startsWith**(prefix)
 
 Checks if the string starts with `prefix`.
 
 It is a runtime error if `prefix` is not a string.
 
+### **trim**()
+
+Returns a new string with whitespace removed from the beginning and end of this
+string. "Whitespace" is space, tab, carriage return, and line feed characters.
+
+    :::wren
+    System.print(" \nstuff\r\t".trim()) //> stuff
+
+### **trim**(chars)
+
+Returns a new string with all code points in `chars` removed from the beginning
+and end of this string.
+
+    :::wren
+    System.print("ᵔᴥᵔᴥᵔbearᵔᴥᴥᵔᵔ".trim("ᵔᴥ")) //> bear
+
+### **trimEnd**()
+
+Like `trim()` but only removes from the end of the string.
+
+    :::wren
+    System.print(" \nstuff\r\t".trimEnd()) //> " \nstuff"
+
+### **trimEnd**(chars)
+
+Like `trim()` but only removes from the end of the string.
+
+    :::wren
+    System.print("ᵔᴥᵔᴥᵔbearᵔᴥᴥᵔᵔ".trimEnd("ᵔᴥ")) //> ᵔᴥᵔᴥᵔbear
+
+### **trimStart**()
+
+Like `trim()` but only removes from the beginning of the string.
+
+    :::wren
+    System.print(" \nstuff\r\t".trimStart()) //> "stuff\r\t"
+
+### **trimStart**(chars)
+
+Like `trim()` but only removes from the beginning of the string.
+
+    :::wren
+    System.print("ᵔᴥᵔᴥᵔbearᵔᴥᴥᵔᵔ".trimStart("ᵔᴥ")) //> bearᵔᴥᴥᵔᵔ
+
 ### **+**(other) operator
 
 Returns a new string that concatenates this string and `other`.
diff --git a/src/vm/wren_core.wren b/src/vm/wren_core.wren
index 2788308c..c2d0af92 100644
--- a/src/vm/wren_core.wren
+++ b/src/vm/wren_core.wren
@@ -236,6 +236,48 @@ class String is Sequence {
     return result
   }
 
+  trim() { trim_("\t\r\n ", true, true) }
+  trim(chars) { trim_(chars, true, true) }
+  trimEnd() { trim_("\t\r\n ", false, true) }
+  trimEnd(chars) { trim_(chars, false, true) }
+  trimStart() { trim_("\t\r\n ", true, false) }
+  trimStart(chars) { trim_(chars, true, false) }
+
+  trim_(chars, trimStart, trimEnd) {
+    if (!(chars is String)) {
+      Fiber.abort("Characters must be a string.")
+    }
+
+    var codePoints = chars.codePoints.toList
+
+    var start
+    if (trimStart) {
+      while (start = iterate(start)) {
+        if (!codePoints.contains(codePointAt_(start))) break
+      }
+
+      if (start == false) return ""
+    } else {
+      start = 0
+    }
+
+    var end
+    if (trimEnd) {
+      end = byteCount_ - 1
+      while (end >= start) {
+        var codePoint = codePointAt_(end)
+        if (codePoint != -1 && !codePoints.contains(codePoint)) break
+        end = end - 1
+      }
+
+      if (end < start) return ""
+    } else {
+      end = -1
+    }
+
+    return this[start..end]
+  }
+
   *(count) {
     if (!(count is Num) || !count.isInteger || count < 0) {
       Fiber.abort("Count must be a non-negative integer.")
diff --git a/src/vm/wren_core.wren.inc b/src/vm/wren_core.wren.inc
index 8251f9f3..63d6648f 100644
--- a/src/vm/wren_core.wren.inc
+++ b/src/vm/wren_core.wren.inc
@@ -238,6 +238,56 @@ static const char* coreModuleSource =
 "    return result\n"
 "  }\n"
 "\n"
+"  trim() { trim_(\"\t\r\n \", true, true) }\n"
+"\n"
+"  trim(chars) { trim_(chars, true, true) }\n"
+"\n"
+"  trimEnd() { trim_(\"\t\r\n \", false, true) }\n"
+"\n"
+"  trimEnd(chars) { trim_(chars, false, true) }\n"
+"\n"
+"  trimStart() { trim_(\"\t\r\n \", true, false) }\n"
+"\n"
+"  trimStart(chars) { trim_(chars, true, false) }\n"
+"\n"
+"  trim_(chars, trimStart, trimEnd) {\n"
+"    if (!(chars is String)) {\n"
+"      Fiber.abort(\"Characters must be a string.\")\n"
+"    }\n"
+"\n"
+"    var codePoints = chars.codePoints.toList\n"
+"//     System.print(\"code points %(codePoints)\")\n"
+"\n"
+"    var start\n"
+"    if (trimStart) {\n"
+"      while (start = iterate(start)) {\n"
+"        if (!codePoints.contains(codePointAt_(start))) break\n"
+"      }\n"
+"\n"
+"      if (start == false) return \"\"\n"
+"    } else {\n"
+"      start = 0\n"
+"    }\n"
+"\n"
+"    var end\n"
+"    if (trimEnd) {\n"
+"      end = byteCount_ - 1\n"
+"      while (end >= start) {\n"
+"        var codePoint = codePointAt_(end)\n"
+"//         System.print(\"test %(end) : %(codePoint)\")\n"
+"        if (codePoint != -1 && !codePoints.contains(codePoint)) break\n"
+"        end = end - 1\n"
+"      }\n"
+"\n"
+"//       System.print(\"range %(start) %(end)\")\n"
+"      if (end < start) return \"\"\n"
+"    } else {\n"
+"      end = -1\n"
+"    }\n"
+"\n"
+"    return this[start..end]\n"
+"  }\n"
+"\n"
 "  *(count) {\n"
 "    if (!(count is Num) || !count.isInteger || count < 0) {\n"
 "      Fiber.abort(\"Count must be a non-negative integer.\")\n"
diff --git a/test/core/string/trim.wren b/test/core/string/trim.wren
new file mode 100644
index 00000000..23c3fc29
--- /dev/null
+++ b/test/core/string/trim.wren
@@ -0,0 +1,16 @@
+System.print("".trim() == "") // expect: true
+System.print("foo".trim() == "foo") // expect: true
+System.print(" \t\r\nfoo b\tar \t\r\n".trim() == "foo b\tar") // expect: true
+System.print(" \t\r\n \t\r\n".trim() == "") // expect: true
+System.print(" \n\n\tsøméஃthîng \n\n\t".trim() == "søméஃthîng") // expect: true
+
+System.print("".trim("abc") == "") // expect: true
+System.print("foo".trim("abc") == "foo") // expect: true
+System.print("foo".trim("") == "foo") // expect: true
+System.print("cbacbfoobarab".trim("abc") == "foobar") // expect: true
+System.print("abcbacba".trim("abc") == "") // expect: true
+System.print("søméஃthîngsøméஃ".trim("ஃmésø") == "thîng") // expect: true
+
+// 8-bit clean.
+System.print(" \t\ra\0b \t\r".trim() == "a\0b") // expect: true
+System.print("\0a\0b\0c\0".trim("c\0a") == "b") // expect: true
diff --git a/test/core/string/trim_chars_not_string.wren b/test/core/string/trim_chars_not_string.wren
new file mode 100644
index 00000000..ae68b819
--- /dev/null
+++ b/test/core/string/trim_chars_not_string.wren
@@ -0,0 +1 @@
+"abracadabra".trim(123) // expect runtime error: Characters must be a string.
diff --git a/test/core/string/trim_end.wren b/test/core/string/trim_end.wren
new file mode 100644
index 00000000..fc082743
--- /dev/null
+++ b/test/core/string/trim_end.wren
@@ -0,0 +1,16 @@
+System.print("".trimEnd() == "") // expect: true
+System.print("foo".trimEnd() == "foo") // expect: true
+System.print(" \t\r\nfoo b\tar \t\r\n".trimEnd() == " \t\r\nfoo b\tar") // expect: true
+System.print(" \t\r\n \t\r\n".trimEnd() == "") // expect: true
+System.print("søméஃthîng \n\n\t".trimEnd() == "søméஃthîng") // expect: true
+
+System.print("".trimEnd("abc") == "") // expect: true
+System.print("foo".trimEnd("abc") == "foo") // expect: true
+System.print("foo".trimEnd("") == "foo") // expect: true
+System.print("cbacbfoobarab".trimEnd("abc") == "cbacbfoobar") // expect: true
+System.print("abcbacba".trimEnd("abc") == "") // expect: true
+System.print("søméஃthîngsøméஃ".trimEnd("ஃmésø") == "søméஃthîng") // expect: true
+
+// 8-bit clean.
+System.print(" \t\ra\0b \t\r".trimEnd() == " \t\ra\0b") // expect: true
+System.print("\0a\0b\0c\0".trimEnd("c\0") == "\0a\0b") // expect: true
diff --git a/test/core/string/trim_end_chars_not_string.wren b/test/core/string/trim_end_chars_not_string.wren
new file mode 100644
index 00000000..929ae08d
--- /dev/null
+++ b/test/core/string/trim_end_chars_not_string.wren
@@ -0,0 +1 @@
+"abracadabra".trimEnd(123) // expect runtime error: Characters must be a string.
diff --git a/test/core/string/trim_start.wren b/test/core/string/trim_start.wren
new file mode 100644
index 00000000..2e1eb3a4
--- /dev/null
+++ b/test/core/string/trim_start.wren
@@ -0,0 +1,16 @@
+System.print("".trimStart() == "") // expect: true
+System.print("foo".trimStart() == "foo") // expect: true
+System.print(" \t\r\nfoo b\tar \t\r\n".trimStart() == "foo b\tar \t\r\n") // expect: true
+System.print(" \t\r\n \t\r\n".trimStart() == "") // expect: true
+System.print(" \n\n\tsøméஃthîng".trimStart() == "søméஃthîng") // expect: true
+
+System.print("".trimStart("abc") == "") // expect: true
+System.print("foo".trimStart("abc") == "foo") // expect: true
+System.print("foo".trimStart("") == "foo") // expect: true
+System.print("cbacbfoobarab".trimStart("abc") == "foobarab") // expect: true
+System.print("abcbacba".trimStart("abc") == "") // expect: true
+System.print("søméஃthîng".trimStart("ஃmésø") == "thîng") // expect: true
+
+// 8-bit clean.
+System.print(" \t\ra\0b".trimStart() == "a\0b") // expect: true
+System.print("\0a\0b\0c\0".trimStart("a\0") == "b\0c\0") // expect: true
diff --git a/test/core/string/trim_start_chars_not_string.wren b/test/core/string/trim_start_chars_not_string.wren
new file mode 100644
index 00000000..8960c7a3
--- /dev/null
+++ b/test/core/string/trim_start_chars_not_string.wren
@@ -0,0 +1 @@
+"abracadabra".trimStart(123) // expect runtime error: Characters must be a string.