.htaccess 301 redirect of single page

Solution 1:

RedirectMatch uses a regular expression that is matched against the URL path. And your regular expression /contact.php just means any URL path that contains /contact.php but not just any URL path that is exactly /contact.php. So use the anchors for the start and end of the string (^ and $):

RedirectMatch 301 ^/contact\.php$ /contact-us.php

Solution 2:

This should do it

RedirectPermanent /contact.php /contact-us.php 

Solution 3:

redirect 301 /contact.php /contact-us.php

There is no point using the redirectmatch rule and then have to write your links so they are exact match. If you don't include you don't have to exclude! Just use redirect without match and then use links normally