Rountree was born in Los Angeles, California. When he was two years old, his father was shot and killed in an attempted robbery while working as the tour manager for Boyz II Men. Growing up overweight and self-described as "non-confrontational," Rountree was in a band traveling the country. Eating unhealthy and smoking cigarettes, he decided to begin training after watching The Ultimate Fighter with his brother. At the age of 20 and weighing 300 lbs., Rountree joined Wand Fight Team gym in an attempt to lose weight. After one year of MMA training, Rountree started his MMA amateur career in 2011. Khalil trains at Syndicate MMA Las Vegas. Before his UFC 236 fight against Eryk Anders, Rountree trained in Thailand, focusing on Muay Thai.
Rountree had a record of 6-1 in his amateur fights, competing as a Middleweight under the Tuff-N-Uff and King of the Cage banners. He amassed a record of 4-0 in his professional career fighting in Resurrection Fighting Alliance prior to joining the UFC.
The Ultimate Fighter
In April 2016, Rountree competed as a fighter on. In the first round, he faced Muhammed DeReese and won via knockout. In the elimination round, he faced Cory Hendricks and lost via submission in the first round. Later in the show, Hendricks withdrew himself from the competition due to neck injury and Dana White decided to bring back Rountree for the semi-final round. Rountree moved on to faced Josh Stansbury and won via knockout in the first round to advance face Andrew Sanchez at the finale.
Rountree made his promotional debut on July 8, 2016 at UFC for the TUF 23 Light Heavyweight title against Andrew Sanchez. He lost the fight via unanimous decision. Rountree next faced Tyson Pedro at on November 27, 2016. He was submitted via rear-naked choke in round one. On his third fight Rountree faced Daniel Jolly at on February 4, 2017. He won via knockout in the first round. Rountree faced Paul Craig on July 16, 2017 at. He won the fight via knockout in the first round. Rountree was expected to face Gökhan Saki on December 30, 2017 at UFC 219. However, Saki was forced to pull out, citing knee injury, and was replaced by Michał Oleksiejczuk. Rountree lost the fight by unanimous decision. However, after the fight, it was revealed that Oleksiejczuk had tested positive for clomiphene, an anti-estrogenic substance. As a result, the Nevada Athletic Commission officially overturned the result of the fight to a no contest. The bout between Rountree and Gökhan Saki eventually took place at UFC 226 on July 7, 2018. Rountree won the fight via knockout in round one. This fight earned him the Performance of the Night award. Rountree faced promotional newcomer Johnny Walker on November 17, 2018 at UFC Fight Night 140. He lost the fight via knockout in the first round. Rountree faced Eryk Anders on April 13, 2019 at UFC 236. He won the fight via unanimous decision. Rountree faced Ion Cuțelaba on September 28, 2019 at UFC on ESPN+ 18. He lost via TKO in the first round. Rountree was expected to face Sam Alvey on March 28, 2020 at. Due to the COVID-19 pandemic, the event was eventually postponed.
