State Road 400 (NM 400) is a 10.620-mile-long (17.091 km) state highway in the US state of New Mexico.

NM 400's southern terminus is at the end of state maintenance where it continues as County Route 50 in McGaffey, and the northern terminus is at NM 118 and Historic US 66 in Wingate.

The entire route is in McKinley County.