diff --git a/README.md b/README.md
index 6e5bb46b..e70598f6 100644
--- a/README.md
+++ b/README.md
@@ -144,8 +144,10 @@ Method                                              | Description
 `contains($value, $subString, $message = '')`       | Check that a string contains a substring
 `notContains($value, $subString, $message = '')`    | Check that a string does not contains a substring
 `startsWith($value, $prefix, $message = '')`        | Check that a string has a prefix
+`notStartsWith($value, $prefix, $message = '')`     | Check that a string does not have a prefix
 `startsWithLetter($value, $message = '')`           | Check that a string starts with a letter
 `endsWith($value, $suffix, $message = '')`          | Check that a string has a suffix
+`notEndsWith($value, $suffix, $message = '')`       | Check that a string does not have a suffix
 `regex($value, $pattern, $message = '')`            | Check that a string matches a regular expression
 `notRegex($value, $pattern, $message = '')`         | Check that a string does not match a regular expression
 `unicodeLetters($value, $message = '')`             | Check that a string contains Unicode letters only
diff --git a/src/Assert.php b/src/Assert.php
index e243cb42..7b58f9d1 100644
--- a/src/Assert.php
+++ b/src/Assert.php
@@ -74,8 +74,10 @@
  * @method static void nullOrNotContains($value, $subString, $message = '')
  * @method static void nullOrNotWhitespaceOnly($value, $message = '')
  * @method static void nullOrStartsWith($value, $prefix, $message = '')
+ * @method static void nullOrNotStartsWith($value, $prefix, $message = '')
  * @method static void nullOrStartsWithLetter($value, $message = '')
  * @method static void nullOrEndsWith($value, $suffix, $message = '')
+ * @method static void nullOrNotEndsWith($value, $suffix, $message = '')
  * @method static void nullOrRegex($value, $pattern, $message = '')
  * @method static void nullOrNotRegex($value, $pattern, $message = '')
  * @method static void nullOrUnicodeLetters($value, $message = '')
@@ -163,8 +165,10 @@
  * @method static void allNotContains($values, $subString, $message = '')
  * @method static void allNotWhitespaceOnly($values, $message = '')
  * @method static void allStartsWith($values, $prefix, $message = '')
+ * @method static void allNotStartsWith($values, $prefix, $message = '')
  * @method static void allStartsWithLetter($values, $message = '')
  * @method static void allEndsWith($values, $suffix, $message = '')
+ * @method static void allNotEndsWith($values, $suffix, $message = '')
  * @method static void allRegex($values, $pattern, $message = '')
  * @method static void allNotRegex($values, $pattern, $message = '')
  * @method static void allUnicodeLetters($values, $message = '')
@@ -1199,6 +1203,26 @@ public static function startsWith($value, $prefix, $message = '')
         }
     }
 
+    /**
+     * @psalm-pure
+     *
+     * @param string $value
+     * @param string $prefix
+     * @param string $message
+     *
+     * @throws InvalidArgumentException
+     */
+    public static function notStartsWith($value, $prefix, $message = '')
+    {
+        if (0 === \strpos($value, $prefix)) {
+            static::reportInvalidArgument(\sprintf(
+                $message ?: 'Expected a value not to start with %2$s. Got: %s',
+                static::valueToString($value),
+                static::valueToString($prefix)
+            ));
+        }
+    }
+
     /**
      * @psalm-pure
      *
@@ -1248,6 +1272,26 @@ public static function endsWith($value, $suffix, $message = '')
         }
     }
 
+    /**
+     * @psalm-pure
+     *
+     * @param string $value
+     * @param string $suffix
+     * @param string $message
+     *
+     * @throws InvalidArgumentException
+     */
+    public static function notEndsWith($value, $suffix, $message = '')
+    {
+        if ($suffix === \substr($value, -\strlen($suffix))) {
+            static::reportInvalidArgument(\sprintf(
+                $message ?: 'Expected a value not to end with %2$s. Got: %s',
+                static::valueToString($value),
+                static::valueToString($suffix)
+            ));
+        }
+    }
+
     /**
      * @psalm-pure
      *
diff --git a/tests/AssertTest.php b/tests/AssertTest.php
index a12a846c..49e9807e 100644
--- a/tests/AssertTest.php
+++ b/tests/AssertTest.php
@@ -295,6 +295,18 @@ public function getTests()
             array('startsWithLetter', array(''), false),
             array('startsWithLetter', array(null), false),
             array('startsWithLetter', array(66), false),
+            array('notStartsWith', array('abcd', 'ab'), false),
+            array('notStartsWith', array('abcd', 'bc'), true),
+            array('notStartsWith', array('', 'bc'), true),
+            array('notStartsWith', array('äþçð', 'äþ'), false),
+            array('notStartsWith', array('äþçð', 'þç'), true),
+            array('notStartsWith', array('', 'þç'), true),
+            array('notStartsWith', array('あいうえ', 'あい'), false),
+            array('notStartsWith', array('あいうえ', 'いう'), true),
+            array('notStartsWith', array('', 'いう'), true),
+            array('notStartsWith', array('😄😑☹️', '😄'), false),
+            array('notStartsWith', array('😄😑☹️', '😑'), true),
+            array('notStartsWith', array('', '😑'), true),
             array('endsWith', array('abcd', 'cd'), true),
             array('endsWith', array('abcd', 'bc'), false),
             array('endsWith', array('', 'bc'), false),
@@ -307,6 +319,18 @@ public function getTests()
             array('endsWith', array('😄😑☹️', '☹️'), true),
             array('endsWith', array('😄😑☹️', '😑'), false),
             array('endsWith', array('', '😑'), false),
+            array('notEndsWith', array('abcd', 'cd'), false),
+            array('notEndsWith', array('abcd', 'bc'), true),
+            array('notEndsWith', array('', 'bc'), true),
+            array('notEndsWith', array('äþçð', 'çð'), false),
+            array('notEndsWith', array('äþçð', 'þç'), true),
+            array('notEndsWith', array('', 'þç'), true),
+            array('notEndsWith', array('あいうえ', 'うえ'), false),
+            array('notEndsWith', array('あいうえ', 'いう'), true),
+            array('notEndsWith', array('', 'いう'), true),
+            array('notEndsWith', array('😄😑☹️', '☹️'), false),
+            array('notEndsWith', array('😄😑☹️', '😑'), true),
+            array('notEndsWith', array('', '😑'), true),
             array('regex', array('abcd', '~^ab~'), true),
             array('regex', array('abcd', '~^bc~'), false),
             array('regex', array('', '~^bc~'), false),