Valu lui Traian (historical name: Hasancea, Turkish: Hasançay) is a commune in Constanța County, Northern Dobruja, Romania.

In 1925 it was renamed Valu lui Traian (Trajan's Wall), after the vallum located nearby.

It is located on top of an archaeological site, remnants of a Roman defensive system, and houses several species of xerophilous plants and shrubs on its slopes.

At the 2011 census, Valu lui Traian had 9,815 Romanians (85.71%), 6 Hungarians (0.05%), 213 Roma (1.86%), 3 Germans (0.03%), 191 Turks (1.67%), 1,189 Tatars (10.38%), 7 Lipovans (0.06%), 20 others (0.17%), 8 with undeclared ethnicity (0.07%).

[5] At the 2021 census Valu lui Traian had a population of 16,617 with a majority of Romanians (74.14%) and minorities of Tatars (6.61%), Turks (1.43%), Roma (1.25%), Lipovans (0.07%), Greeks (0.06%), Bulgarians (0.02%), others (0.23%) and unknown (16.19%).