diff --git a/builtin/core.wren b/builtin/core.wren
index d1e406d6..54b48f3b 100644
--- a/builtin/core.wren
+++ b/builtin/core.wren
@@ -42,6 +42,20 @@ class Sequence {
     return result
   }
 
+  join { join("") }
+
+  join(sep) {
+    var first = true
+    var result = ""
+
+    for (element in this) {
+      if (!first) result = result + sep
+      first = false
+      result = result + element.toString
+    }
+
+    return result
+  }
 }
 
 class String is Sequence {}
@@ -54,15 +68,7 @@ class List is Sequence {
     return other
   }
 
-  toString {
-    var result = "["
-    for (i in 0...count) {
-      if (i > 0) result = result + ", "
-      result = result + this[i].toString
-    }
-    result = result + "]"
-    return result
-  }
+  toString { "[" + join(", ") + "]" }
 
   +(other) {
     var result = this[0..-1]
diff --git a/doc/site/core/sequence.markdown b/doc/site/core/sequence.markdown
index 4ed8c942..af55277e 100644
--- a/doc/site/core/sequence.markdown
+++ b/doc/site/core/sequence.markdown
@@ -18,6 +18,17 @@ If it returns `false`, stops iterating and returns `false`. Otherwise, returns
     [1, 2, 3].all {|n| n > 2} // False.
     [1, 2, 3].all {|n| n < 4} // True.
 
+### **join**(sep)
+
+Returns a string representation of the list. The string representations of the
+elements in the list is concatenated with intervening occurrences of `sep`.
+
+It is a runtime error if `sep` is not a string.
+
+### **join**
+
+Calls `join` with the empty string as the separator.
+
 ### **map**(transformation)
 
 Creates a new list by applying `transformation` to each element in the
diff --git a/src/wren_core.c b/src/wren_core.c
index b551f701..d8db5cf5 100644
--- a/src/wren_core.c
+++ b/src/wren_core.c
@@ -85,6 +85,20 @@ static const char* libSource =
 "    return result\n"
 "  }\n"
 "\n"
+"  join { join(\"\") }\n"
+"\n"
+"  join(sep) {\n"
+"    var first = true\n"
+"    var result = \"\"\n"
+"\n"
+"    for (element in this) {\n"
+"      if (!first) result = result + sep\n"
+"      first = false\n"
+"      result = result + element.toString\n"
+"    }\n"
+"\n"
+"    return result\n"
+"  }\n"
 "}\n"
 "\n"
 "class String is Sequence {}\n"
@@ -97,15 +111,7 @@ static const char* libSource =
 "    return other\n"
 "  }\n"
 "\n"
-"  toString {\n"
-"    var result = \"[\"\n"
-"    for (i in 0...count) {\n"
-"      if (i > 0) result = result + \", \"\n"
-"      result = result + this[i].toString\n"
-"    }\n"
-"    result = result + \"]\"\n"
-"    return result\n"
-"  }\n"
+"  toString { \"[\" + join(\", \") + \"]\" }\n"
 "\n"
 "  +(other) {\n"
 "    var result = this[0..-1]\n"
diff --git a/test/list/join.wren b/test/list/join.wren
new file mode 100644
index 00000000..12a39307
--- /dev/null
+++ b/test/list/join.wren
@@ -0,0 +1,23 @@
+// Handle empty list.
+IO.print([].join(",") == "") // expect: true
+
+// Handle a simple list with an empty delimeter.
+IO.print([1, 2, 3].join("")) // expect: 123
+
+// Handle a simple list with no separator.
+IO.print([1, 2, 3].join) // expect: 123
+
+// Does not quote strings.
+IO.print([1, "2", true].join(",")) // expect: 1,2,true
+
+// Nested lists.
+IO.print([1, [2, [3], 4], 5].join(",")) // expect: 1,[2, [3], 4],5
+
+// Calls toString on elements.
+class Foo {
+  toString { "Foo.toString" }
+}
+
+IO.print([1, new Foo, 2].join(", ")) // expect: 1, Foo.toString, 2
+
+// TODO: Handle lists that contain themselves.
diff --git a/test/list/join_sep_non_string.wren b/test/list/join_sep_non_string.wren
new file mode 100644
index 00000000..d63d83f4
--- /dev/null
+++ b/test/list/join_sep_non_string.wren
@@ -0,0 +1 @@
+[1, 2, 3].join(2) // expect runtime error: Right operand must be a string.
diff --git a/test/range/join.wren b/test/range/join.wren
new file mode 100644
index 00000000..81c336a1
--- /dev/null
+++ b/test/range/join.wren
@@ -0,0 +1,4 @@
+var a = 1..3
+
+IO.print(a.join) // expect: 123
+IO.print(a.join(", ")) // expect: 1, 2, 3
diff --git a/test/range/join_sep_non_string.wren b/test/range/join_sep_non_string.wren
new file mode 100644
index 00000000..7dfccf99
--- /dev/null
+++ b/test/range/join_sep_non_string.wren
@@ -0,0 +1 @@
+(1..3).join(2) // expect runtime error: Right operand must be a string.
diff --git a/test/string/join.wren b/test/string/join.wren
new file mode 100644
index 00000000..6c1183c1
--- /dev/null
+++ b/test/string/join.wren
@@ -0,0 +1,5 @@
+var str = "string"
+
+IO.print(str.join("") == str) // expect: true
+
+IO.print(str.join(", ")) // expect: s, t, r, i, n, g
diff --git a/test/string/join_sep_non_string.wren b/test/string/join_sep_non_string.wren
new file mode 100644
index 00000000..feaaa5aa
--- /dev/null
+++ b/test/string/join_sep_non_string.wren
@@ -0,0 +1 @@
+"string".join(2) // // expect runtime error: Right operand must be a string.