Warren Sapp has just been charged with 3 counts of domestic violence stemming from an incident in Las Vegas ... where officials say he bit and stomped on his girlfriend's head ... TMZ Sports has learned. According to official documents obtained by TMZ Sports ... Sapp attacked his longtime girlfriend, Chalyce Moore, on April 28th at the M Resort in Las Vegas. According to the police report, the two had been arguing ... and Sapp allegedly threw a margarita in her face in their private cabana by the pool. Sapp allegedly grabbed Chalyce by the arm or purse and violently pulled on her ... nearly taking her down to the ground. The couple left the resort together in a car -- heading toward Chalyce's condo. During the car ride, the Chalyce says she got sick of arguing and told Sapp to get out of the car ... but he responded by BITING HER MIDDLE FINGER. At one point, Sapp got out of the car and asked another driver for a ride. The driver denied his request. According to the docs, they got back in the car together and eventually got to the condo -- where the violence continued. Once inside, Sapp allegedly threw a belt at her ... and she threw it back at him ... and during the altercation, she ended up on the floor. While she was down, Chalyce claims Sapp stepped on her face while wearing white Jordan sandals. Sapp is approximately 6'2", 300 lbs and wears size 15 shoes. Cops say they went to the M Resort and watched security footage that backed up her story. They now have that video. Chalyce's friend told police that Sapp's GF has sustained multiple injuries -- including a bruise on her lower lip, abrasions and bruises on her shoulders, bruising on her legs, and a bruise on one of her temples with a checkerboard imprint (presumably from Sapp's Jordan sandals). Moore also told investigators she thinks she suffered a concussion because she had a stiff neck, headache and was vomiting after the incident. Sapp is facing 3 counts of battery constituting domestic violence -- if convicted on all counts he could face up to 18 months in prison. He's due in court on July 23rd. By the way, those size 15 Jordan sandals? Sapp was wearing them when Phoenix cops interviewed him about assaulting 2 prostitutes.