About how many million years ago did the Indian Plate begin colliding with Eurasia to form the Himalayas?

The Indian Plate began colliding with Eurasia about 50 million years ago, initiating the formation of the Himalayas.

Before the collision, the Indian Plate moved northward across the former Tethys Ocean. As it converged with the Eurasian Plate, oceanic crust was consumed and sediments were compressed, folded, and uplifted into mountain belts.

The collision did not create the entire modern landscape instantly. Uplift, erosion, earthquakes, and continuing plate convergence have shaped the range over tens of millions of years. India still moves northward relative to Eurasia, so the Himalayas remain tectonically active.

The exact age assigned to the collision varies among geological studies because researchers use different evidence and definitions for its beginning. About 50 million years ago is the standard broad figure, not a claim that every Himalayan rock formed at that moment.