NEW DELHI — Tehmina Yadav is a Muslim woman married to a Hindu man. The other night, she was hanging ornaments on a Christmas tree.

In India, a country that is about 80 percent Hindu, Christmas is becoming big business. Airlines play Christmas music, online vendors sell holiday gift baskets, and one especially enterprising young man, Kabir Mishra, rents out a contingent of Hindus dressed as Santa Claus.

“I can provide as many Santas as you want,” he said.

Sitting next to her Christmas tree at home in Delhi, Ms. Yadav said that in India, there was nothing strange about non-Christians celebrating Christmas. Indians have always observed a dizzying number of festivals regardless of religious affiliation, and even though Christians represent only 2.3 percent of the population, Christmas is recognized as a government holiday.

But as far-right Hindu groups have gained traction, India has changed. Christmas has now found itself caught in the cross hairs.