County Road 340 (CR 340) is a county road in Rio Arriba County, New Mexico, United States, that connects New Mexico State Road 531 (NM 531) and NM 572 in La Puente with NM 514 in Los Ojos.
CR 340 begins at a T-intersection with NM 531 and NM 572 in the unincorporated community of La Puente.
From its southern terminus CR 340 heads northeasterly as a two-lane asphalt paved road southeast of, but roughly parallel to, the Rio Chama. About from its southern terminus, CR 340 reaches its northern terminus at a T-intersection with NM 514 (Main Street) in Los Ojos.