古螺城 (越南语：Thành Cổ Loa／城古螺)是河内以北约20公里的一座古代城堡，鸿庞氏末期（约公元前257年）。

据民间传说，公元前257年，蜀泮击败了最后的雄王，创建了瓯雒国，选择红河三角洲北部河漫滩的古螺城作为新首都。这座城堡是一个螺旋形的巨大建筑群，修建时动用了大量的劳动力和资源。

古螺城包括外侧的两层城墙，和内侧的长方形城堡。外城墙周长8公里，高12米，底部宽25米。考古学家估计，构建整个要塞，运输了超过200万立方米的材料。

Cổ Loa Citadel (Vietnamese:Thành Cổ Loa) is a citadel in present-day Hanoi's Dong Anh district, about 16 kilometers (10 mi) northeast of downtown. It was erected during the end of the Hồng Bàng Dynasty (about 257 BCE). The fortress is a spiral-shaped complex of the then new capital. Its name is derived from the Sino-Vietnamese 古螺, meaning "old spiral." The site has been the source of various relics of the Dong Son culture of the Bronze Age.