The relationship between Nike and the Grand Slam champion dates back to when she was 11-years-old.
Sharapova tested positive for meldonium, which she stated she had been taking for health issues since 2006. The substance was banned by the World Anti-Doping Agency (WADA), because it can enhance oxygen uptake in the body and endurance, on 1st January.
Nike said: "We have decided to suspend our relationship with Maria while the investigation continues. We will continue to monitor the situation."
Swiss watch brand Tag Heuer has also decided not to renew its contract with the 28-year-old which ran out at the end of last year.
She is believed to be the world’s highest paid female athlete, with estimated earnings of £20.7m in 2015 and has contracts with the likes Evian, Porsche and American Express.