Radio 21 was a Portuguese radio station known for its alternative and rock music programming. It operated in the early 2000s, offering a distinct selection of music that catered to niche audiences and diverged from mainstream radio trends in Portugal. Despite its unique style and dedicated listener base, the station ceased operations in 2004. Its closure was attributed to financial difficulties and challenges in maintaining a competitive market presence. Radio 21 remains remembered for its contribution to Portugal's alternative music scene.