Rhymester (ライムスター, Raimu Sutā) is a Japanese hip hop group consisting of MCs Mummy-D and Utamaru, and DJ Jin. The group is one of the oldest Japanese hip hop acts, having formed in 1989. They debuted on an independent label in 1993 with the EP Ore ni Iwaserya (俺に言わせりゃ), which was panned by critics. Later on, they released several studio albums and gradually became popular among not only hip hop fans but also rock fans, as they frequently collaborated with rock musicians such as Kiyoshiro Imawano. In 2001, the group made their major label debut when they signed onto Ki/oon Records, a sublabel of Sony Music Entertainment Japan. On March 3, 2007, the group performed solo at the Nippon Budokan, almost 20 years after their original debut.

The single HEAT ISLAND featuring FIRE BALL was featured in the anime series Ayakashi: Japanese Classic Horror. Rhymester has released several songs such as "B-Boyism" (B-BOYイズム), "Mimi wo Kasubeki" (耳ヲ貸スベキ), "King Of Stage", "Nikutai-Kankei" (肉体関係) and more.