The leopard, said to be around four-year-old, was killed last night when it was hit by some vehicle in Katarniaghat Wildlife Sanctuary area, forest officials said.
Project officer of WWF, Dabeer Hasan said a panel of doctors would conduct the post-mortem tomorrow to ascertain cause of death.
He said as per 2005 counting, there are 32 leopards in the Sanctuary.
The Katarniaghat Wildlife Sanctuary is a protected area, spread over in around 400 square km, in the upper Gangetic plain in Uttar Pradesh's Bahraich district.