Myeonghwalseong (Korean: 명활성; Hanja: 明活城) or Myeonghwalsanseong (명활산성; 明活山城) was a Silla-era Korean fortress on the mountain Myeonghwalsan in what is now Gyeongju, South Korea.

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

There is a record in the Samguk sagi of the fortress being attacked in 405 AD (Korean calendar).

Archaeological digs have identified six sites where buildings likely once stood.

From 2012 to 2014, another survey was conducted, which found further evidence that the fortress was reconstructed a number of times.