Jason Anthony "The Athlete" MacDonald (born June 3, 1975) is a Canadian mixed martial artist who competes as a middleweight in the Ultimate Fighting Championship. Born and raised in Merigomish, Pictou County, Nova Scotia, MacDonald currently resides in Red Deer, Alberta and fights out of Edmonton, Alberta.

MacDonald made his UFC debut on October 10, 2006 at Ortiz vs. Shamrock 3: The Final Chapter with a win over the heavily favored The Ultimate Fighter 3 finalist Ed Herman via triangle choke in the first round. On December 30, 2006, at UFC 66, MacDonald defeated Chris Leben with a modified guillotine choke submission in the second round.

Other notable wins include victories over UFC veterans Joe Doerksen, Gideon Ray, and Bill Mahood. Before fighting in the UFC, MacDonald had tried out for The Ultimate Fighter reality television show on multiple occasions, but did not make the cut.

At UFC 68: The Uprising on March 3, 2007, MacDonald fought former UFC Middleweight Champion Rich "Ace" Franklin in Franklin's return bout since losing his title. Franklin mounted MacDonald in the final seconds of round two, causing enough injury to MacDonald's left eye area that his corner advised him to throw in the towel, and Franklin was declared the winner.

At UFC 72, MacDonald defeated Rory Singer (an Ultimate Fighter alum) via TKO (referee stoppage) in the second round.

On October 20, 2007, MacDonald faced Yushin Okami at UFC 77 and was defeated via unanimous decision.

At UFC 83 on April 19, 2008 MacDonald defeated Joe Doerksen via TKO (strikes) at 0:56 of the 2nd round. This win resulted in MacDonald being awarded a $75,000 bonus for Knockout of the Night.

There was controversy as he hit Doerksen with two hammer fists after the fight appeared to have already been stopped. In an interview the day after the fight, Jason explained that the referee admitted to making an error when he instructed Jason to keep going.

On August 9, 2008 at UFC 87 in Minneapolis, Minnesota, Jason lost to Demian Maia at 2:44 of the third round by rear naked choke. Only a month later, he went on to fight as a replacement for Jason Day at UFC 88. He won against Jason Lambert at 1:20 of round 2 by rear naked choke and he also won Submission of the night.

Finishing a busy 2008, MacDonald lost to Wilson Gouveia by submission due to elbow strikes at 2:18 of the first round at the TUF8 Finale. Gouveia dropped MacDonald with a glancing left jab before raining elbows to finish the fight.