The Honda Civic Mugen Si is a factory-modified version of the Honda Civic Si sedan in the US.

• "The Civic Mugen Si starts with the Si sedan and adds a stiffer suspension (which also lowers the vehicle 0.6 inches), 18-inch forged alloy wheels, a full aerodynamic body kit with adjustable rear wing spoiler, a rear diffuser, and a sport-tuned exhaust system claimed to reduce back pressure downstream from the catalytic converter."— JB car pagesJB car pages: 2008 Honda Civic Review