The M21 highway (Romanian: Drumul național M21) was a road in Moldova, which linked Chișinău to the border with Ukraine near Dubău via Dubăsari.

It was 60 km (37 mi) long, and formed part of the European route E584 of the International E-road network.

[2] The M21 highway began at an intersection with the R1 road west of the capital city of Chișinău.

The road then crossed the Dniester to reach the unrecognized state of Transnistria.

[5] Immediately after entering the Transnistrian territory, the road reached a roundabout with the M4 highway, which provides access to Dubăsari, which the M21 bypassed in the south-east.