Tucumcari Mountain, Mountain summit in Quay County, New Mexico, United States.

Tucumcari Mountain is a mesa just outside the town of Tucumcari, New Mexico, once also called Tucumcari Peak or Mesa Tucumcari. Its flat-topped form rises above the surrounding plains, and a hillside letter T painted by town residents marks the slope.

Tucumcari Mountain guided Puebloan, Plains Indian and Comanchero travellers, and the Comanche climbed it to scan for game. Pedro Vial noted it in 1793 while opening the Santa Fe–St. Louis trail, and Randolph B. Marcy passed in 1849. Jules Marcou dated its strata to the Jurassic in 1853, but Robert T. Hill and William F. Cummins showed in 1891 that the beds are Cretaceous.

The town of Tucumcari was founded in 1901 and took its name from the mountain in 1908. Residents have painted a hillside letter T on the mountain, and a cartoon version of it appears in the film Cars, with "RS" for Radiator Springs replacing the T.

Access to the summit is limited to unpaved mountain roads that become hazardous during rain or wet conditions. Plan your visit for dry weather and bring a vehicle suitable for rough terrain if you wish to reach the top.

The mountain contains rock layers from the Cretaceous period, though they were initially misidentified as Jurassic by geologist Jules Marcou in the 1850s. This early geological confusion reflects how scientific understanding of the area has evolved over time.