Maardu (Estonian: [ˈmɑːrd̥u], German: Maart) is a town and a municipality in Harju County, Estonia.

It is part of Tallinn metropolitan area, located about 15 kilometres (9.3 mi) east of the capital city.

61.7% were Russians, 19.9% Estonians, 6.6% Ukrainians, 5.7% Belarusians, 1.5% Tatars.

Outside the town (in the village of Maardu), south of the road to Narva lies Maardu manor, one of the oldest preserved baroque manor houses in Estonia.

It traces its origins to 1389, but the current building dates from the 1660s with additions made in the 19th century.