Marcus Ulf Johan "Bosse" Grönholm is a Finnish former rally and rallycross driver, being part of a family of the Swedish-speaking population of Finland lineage. His son, Niclas Grönholm, is an upcoming FIA World Rallycross Championship driver. Grönholm's nicknames are either "Bosse" or "Magic Marcus". Grönholm is one of the most successful WRC drivers of all time, ranking third in rally wins (30), and winning two championships, in 2000 and 2002. After Peugeot withdrew from the World Rally Championship, Grönholm moved to Ford for the 2006 season and placed second in the drivers' world championship, losing out to Sébastien Loeb by one point. The next year he again placed second, four points behind Loeb. He and his co-driver Timo Rautiainen retired from rallying after the 2007 season but returned to the championship in 2009 driving a private Subaru for a short period of time, and in the 2019 World Rally Championship where he competed in a Toyota Gazoo Racing WRT-maintained Toyota Yaris under the GRX Team banner.

Rallying is a wide-ranging form of motorsport with various competitive motoring elements such as speed tests, navigation tests, or the ability to reach waypoints or a destination at a prescribed time or average speed. Rallies may be short in the form of trials at a single venue, or several thousand miles long in an extreme endurance rally.