User blog comment:Speculation no Kyojin/Episode 25 - The Titan in the wall/@comment-49.145.101.115-20140517121437/@comment-64.233.173.208-20150816051205

Levi's last name is Ackerman, it's revealed in the manga. Rivaille is just a misunderstanding since 'Levi' in Katakana is written 'Rivai'.