Fashion designer, L'Wren Scott, has been found dead at her 11th Avenue apartment in Manhattan.
49 year old, Scott, was found at 10.00 local time by her assistant (14.00 GMT), according to BBC News.
Police are said to be treating it as a suicide, yet no official statement has been released.
Jagger, who is currently in Australia with the Rolling Stones for a tour due to start on Wednesday, had been dating Scott since 2001, following a split from his then wife Jerry Hall. A spokesperson close to Mr. Jagger said that the singer is "completely shocked and devastated" by the news of L'Wren's passing.