Does the rio bravo form part of border between us and Mexico?

Yes, the Rio Bravo (known as the Rio Grande in the United States) does form part of the border between the United States and Mexico. The river constitutes approximately 1,951 miles (3,139 kilometers) out of the total 1,989 miles (3,201 kilometers) of the US-Mexico border.

From its headwaters in Colorado, the Rio Grande/Rio Bravo flows along the New Mexico-Texas border before turning southeast to eventually become a major international boundary between the United States and Mexico.

The remaining parts of the border consist of land barriers and other natural landmarks marking the separation between the two countries.