Mach Speed (ブーストダッシュ Būsuto Dasshu?, lit. "Boost Dash") is a move used by Sonic the Hedgehog that, when activated, gives Sonic a short boost of speed. It has only appeared in Sonic the Hedgehog (2006) as one of Sonic's Custom Actions. It can only be used after Sonic obtains the Blue Gem.
When using this move, Sonic can perform a fast, but very brief "Super Sonic Boost Dash" that increases his speed to its maximum. If Sonic runs into an obstacle while dashing, he will fall down on the ground for a few seconds before getting up.
- The mechanics of the Mach Speed are similar to the Super-Speed Stages sections found in certain action stages of Sonic the Hedgehog (2006), though Sonic does not lose any Rings when he collides with objects.
- When ramming into something with Mach Speed, a glitch will occur where blue winds will still appear around Sonic while he runs at very slow speed.
- In real-life, the term "Mach Speed" derives from the word "Mach Number" which is actually a ratio of a body moving at the speed of sound.
- This move functions similarly to the Speed Up special attack in the multiplayer mode of Sonic Adventure 2.