Namsansinseong (Korean: 남산신성; Hanja: 南山新城) was a Silla-era Korean fortress located on the mountain Namsan in what is now Gyeongju, South Korea.

On January 21, 1963, its location was made Historic Site of South Korea No.

[1][2] According to the Samguk sagi, it was built in 591 (Korean calendar), during the reign of King Jinpyeong.

It was significantly renovated in 679, during the reign of King Munmu.

[1] Currently much of the fortress is in ruins; parts of the wall remain.