Busosanseong (Korean: 부소산성; Hanja: 扶蘇山城) was a Baekje-era Korean fortress on the mountain Busosan in what is now Buyeo County, South Chungcheong Province, South Korea.

On January 21, 1963, it was designated Historic Site of South Korea No.

5.

The fortress was built in 538 (Korean calendar), possibly in place of another existing fortification on the spot, to protect the final Baekje capital Sabi.

The fortification has traces of three main gates and a military depot.