diff --git a/README.markdown b/README.markdown
index dc444939..776b054f 100644
--- a/README.markdown
+++ b/README.markdown
@@ -418,6 +418,17 @@ camelize("Moz-transform");
 camelize("-moz-transform", true);
 // => "mozTransform"
 ```
+#### decamelize(string, [seperator="_"]) => string
+
+Converts camelized string to a decamelized one. 
+
+```javascript
+decamelize("theDecamelizeStringMethod");
+// => "the_decamelize_string_method"
+
+decamelize("webkitTransform", "-");
+// => "webkit-transform"
+```
 
 #### classify(string) => string
 
diff --git a/decamelize.js b/decamelize.js
new file mode 100644
index 00000000..55910ba4
--- /dev/null
+++ b/decamelize.js
@@ -0,0 +1,12 @@
+var decap = require('./decapitalize');
+var trim  = require('./trim');
+
+module.exports = function decamelize(string, separator) {
+	string = trim(string).split(/(?=[A-Z])/).map(function(word) {
+		return decap(word);
+	});
+	if (separator === undefined) {
+		separator = "_";
+	} 
+    return string.join(separator);
+};
diff --git a/index.js b/index.js
index 7e570318..ba6659c8 100644
--- a/index.js
+++ b/index.js
@@ -42,6 +42,7 @@ s.pred             = require('./pred');
 s.succ             = require('./succ');
 s.titleize         = require('./titleize');
 s.camelize         = require('./camelize');
+s.decamelize       = require('./decamelize');
 s.underscored      = require('./underscored');
 s.dasherize        = require('./dasherize');
 s.classify         = require('./classify');
diff --git a/tests/decamelize.js b/tests/decamelize.js
new file mode 100644
index 00000000..24ab5823
--- /dev/null
+++ b/tests/decamelize.js
@@ -0,0 +1,15 @@
+var equal = require('assert').equal;
+var decamelize = require('../decamelize');
+
+
+test('#decamelize', function(){
+  equal(decamelize('theDecamelizeStringMethod'), 'the_decamelize_string_method');
+  equal(decamelize('webkitTransform', '-'), 'webkit-transform');
+  equal(decamelize('theDecamelizeStringMethod_', ''), 'thedecamelizestringmethod_');
+  equal(decamelize('TheDecamelizeStringMethod', '-'), 'the-decamelize-string-method');
+  equal(decamelize(''), '', 'Decamelize empty string returns empty string');
+  equal(decamelize(null), '', 'Decamelize null returns empty string');
+  equal(decamelize(undefined), '', 'Decamelize undefined returns empty string');
+  equal(decamelize(123), '123');
+});
+