Orlando looked set to snatch all three points at Audi Field in Washington on Sunday, when United goalkeeper David Ousted pushed forward for a corner and vacated an empty net.
Will Johnson broke free on the counter and had the goal at his mercy, looking to break the deadlock and hand the Lions a much-needed win.
But Rooney was the man of the moment.
The 32-year-old chased back at top speed and won a last-ditch tackle just inside his own half line to prevent a certain winner.
Even that wasn't enough for Rooney.
His sliding challenge triggered an unbelievable sequence as Man United and England's all-time leading scorer then got to his feet and raced forward before playing a stunning long ball to Luciano Acosta, who rose highest to complete his hat trick in the sixth minute of stoppage time.
WHAT. A. MOMENT. pic.twitter.com/KXfFV9NuEV— Major League Soccer (@MLS) August 13, 2018
It was an incredible passage of play that defied Rooney's age and extended his side's unbeaten streak to three matches.
The win also boosts D.C. United's playoff hopes in the Eastern Conference, with the club still nine points back of sixth place, but with a back-loaded home schedule and games in hand on the other playoff contenders.