Messier 33 (M33), also known as the Triangulum Galaxy, is a spiral galaxy located in the constellation Triangulum, approximately 2.73 million light-years from Earth. It is the third-largest galaxy in the Local Group, following the Andromeda Galaxy (M31) and the Milky Way. With a diameter of about 60,000 light-years, M33 is smaller than its counterparts but features a prominent, loosely wound spiral structure with bright star-forming regions, particularly the giant H II region NGC 604. 

M33 contains an estimated 40 billion stars and has a relatively low surface brightness, making it visible to the naked eye only under very dark skies. Its proximity to Andromeda suggests a possible gravitational interaction, influencing its structure. As an active region for studying stellar evolution, M33's rich star clusters and nebulae provide astronomers with insights into galaxy formation and dynamics in the universe.