Mephiles the Dark (闇のメフィレス Yami no Mefiresu?) (pronounced [mɛfɨləs] or [mə'fɪliːz] in English) is one of the main antagonists of the 2006 video game Sonic the Hedgehog. He is the conscience, mind, and will of the sun god Solaris, ultimately making him the main antagonist of the game's story.

Mephiles is the final boss of Shadow the Hedgehog's story, although he plays a pivotal role in all three of the game's storylines. He is a cunning manipulator, tricking Silver the Hedgehog into believing that Sonic the Hedgehog was the Iblis Trigger and that killing him would save Silver's future. He also has a particular interest in Shadow, who originally imprisoned him after his creation, and whose appearance and powers Mephiles absorbed upon his release. Mephiles repeatedly attempted to convince Shadow to join him, but Shadow refused each time.

He is famous for being the only character in the Sonic the Hedgehog series to actually succeed in killing Sonic. However, as time was erased at the end of the game, this event never actually happened.

Mephiles as compared to Shadow. Note the color differences. Oddly, Mephiles' muzzle has jagged edges, but it may be due to an incomplete character model.