Mud flaps, or also known as mud guards and splash guards are rubber mats which are attached directly behind the wheels of automobiles. As the name implies, mud flaps serve to shield cars from mud and other debris flung out by tires. Most mud flaps are made of high-grade plastic while some are made of metal. It is essential that both rear and front tires be outfitted with mud flaps as road debris will be kicked up and small stones being thrown by the tires may cause scratches and other damages to vehicles and other vehicles from behind. Mud flaps are rather easy to install, but can sometimes prove to be a very messy and awkward process. Just a few bolts or screws are enough to hold the top of the mud flap firmly in place while the bottom edge remains unattached.

With mud guards, mud, snow, slush, and other road debris are kept within the vehicle's wheel. The more debris being blocked from damaging a vehicle's finish, the lesser the likelihood of paint damage and rust or corrosion problems. Although they are commonly called mud flaps, mud guards and splash guards, these rubber mats also help deflect loose gravel and excessive rainwater. Thus, mud flaps may certainly prove handy during heavy rains and other extreme driving conditions.

Like many other after-market vehicle accessories, mud flaps have now become popular means of self-expression. Most automotive supply stores sell a variety of mud flaps which feature cartoon characters, famous logos, artworks, quotations akin to bumper stickers. There are even some companies who actually manufacture custom mud flaps with their name and contact information on it.