Arjen Anthony Lucassen (born 3 April 1960, Hilversum) is a progressive metal/rock songwriter, producer, singer and multi-instrumentalist musician from the Netherlands, best known for his long-running progressive opera project titled Ayreon.

Lucassen plays a wide variety of instruments. His main instruments are guitar and keyboards. But he also plays: bass and banjo. He is also the creator and member of Star One, Guilt Machine, the currently inactive band Ambeon, and the creator and former member of Stream of Passion.
Overall, in his career and including all his bands and projects (as principal instrumentalist/creative force or as a member), Lucassen has released twenty studio albums, two live albums, four EPs and seventeen singles. He has also made many minor participations alongside various artists, and the number of studio albums that include Lucassen is more than 50.
Since the creation of Ayreon, Lucassen progressively gained notoriety to rock and metal reviewers, with many critics calling him a "genius", and praised his composition abilities and originality.