Marcelo Garcia has been diagnosed with stomach cancer ©Marcelo Garcia

Brazilian jiu-jitsu great Marcelo Garcia, regarded as one of the best submission grapplers in history, has been diagnosed with stomach cancer.

The 40-year-old confirmed on Instagram he would be undergoing chemotherapy and surgery to remove the tumour.

Captioned beside a photo of him with his family, Garcia asked for his fans' thoughts and prayers.

"I'm about to fight the biggest fight of my life, I have stomach cancer and will start chemo for 3 months and back at MSK for surgery remove the tumour," he said.

"Please keep me and my family on your prayers. 

"Get your check-ups, listen to your body, all I had was hiccups after eating and I'm glad I went to see a doctor.

"Just wanted to say thank you for everyone who's supporting me now, you all know who you are and I will never forget it."

Garcia is an Abu Dhabi Combat Club (ADCC) and International Brazilian Jiu-Jitsu Federation (IBJJF) Hall of Famer, having won four world titles at the ADCC Submission Fighting World Championships and five IBJFF World Championship titles.

ONE Championship chief executive Chatri Sityodtong and promising grappling twins Kade and Tye Ruotolo were among those to extend their well wishes.

Some regard Garcia as the best pound-for-pound submission grappler in the world.