Selena Gomez has revealed she underwent a kidney transplant, with her friend Francia Raisa donating the organ.

She shared an image of the two in hospital beds hooked up to medical equipment, thanking her actress friend for the "ultimate gift and sacrifice".

The US singer and actress explained to her fans she has been "laying low" this summer because she underwent the major operation due to suffering from the autoimmune disease lupus.

She shared the news and pictures with her 126 million Instagram followers.

She thanked her family and the medical team for their work before and after the surgery adding she was looking forward to sharing her recent journey with her fans.

Gomez said that lupus "continues to be very misunderstood but progress is being made" and directed her fans to the Lupus Research Alliance website.

While Gomez did not give any details about when the operation took place, the Come & Get It hit-maker appeared at a high-profile party at New York Fashion Week on Saturday.