There are at least three bands that go by this name:
1. The US post-rock, shoegaze band are originally from Richmond, Virginia, and now based in Brooklyn. They formed in 2000, took their name from writer Franz Kafka - author of the short story The Metamorphosis. The current members are Champ Bennett, Nikki King, Billy Bennett, Jeremiah Klinger, Cory Bise, Toby Driver and Mia Matsumiya. After the release of two EPs, Gregor Samsa and 27:36, and two splits with The Silent Type and Red Sparowes, Gregor Samsa delivered their much anticipated debut full-length 55:12, composed of eight songs submerged in dreamy, multi-layered post-rock atmospherics. In their next album, Gregor Samsa took a new approach to composition, both in process and instrumentation. The result was Rest, released in May of 2008 on Kora Records (US) and Own Records (Europe).
http://www.gregorsamsa.com
2. There is also a funk-rock band from Prague, Czech Republic called Gregor Samsa. All of the members are Hungarians from Slovakia, and the lyrics are sung in Hungarian.
http://www.gregorsamsa.cz
3. This is also the name of a Japanese industrial band from Tokyo. Read more on Last.fm.