To which clan did Siddhartha Gautama belong?

Siddhartha Gautama belonged to the Shakya clan.

The Shakyas were an ancient tribal confederacy in the Himalayan foothills, with their capital traditionally identified as Kapilavastu. Siddhartha’s father, Śuddhodana, was a leading figure of this community, while his mother, Māyā, came from the related Koliya clan. After enlightenment, Gautama was often called Śākyamuni, meaning “Sage of the Shakyas.”

The Shakya polity was not quite a centralized kingdom in the modern sense. It is commonly described as an aristocratic republic or oligarchic clan assembly, and Śuddhodana may have been an elected leader rather than an absolute king. The Shakyas lived near Kosala and maintained close family links with the Koliyas across the Rohiṇī River.

A common mix-up is to identify Gautama as Koliya because his mother belonged to that neighboring clan. His paternal clan identity, however, was Shakya.