It's a truly remarkable record and means that with Rio set to be his last Olympics, the American is likely to go down as the best Olympic athlete of all time.
HE'S TIED A 2,168-YEAR-OLD OLYMPIC RECORD
As a man who knows little else other than victory, Phelps is used to breaking numerous records along the way.
But incredibly, his gold in the pool on Thursday actually saw the American tie an Olympic record which dates all the way back to 152 BC.
He's now level pegging with Leonidas of Rhodes in terms of the highest number of individual Olympic medals. Not bad going, that.
BUT PHELPS IS FOUR YEARS QUICKER THAN HIS ANCIENT RIVAL
It's a pretty strange situation when you're comparing a modern day athlete to an ancient rival from thousands of years ago.
But when someone breaks records like Phelps does, it has to be done.
He is now level with Leonidas in terms of the number of golds but he's done it four years quicker.
MOVE ASIDE, JESUS!
Phelps is used to breaking world records and more in the 21st century.
But now he's tied with Leonidas, it means he's equalled a record that existed before Jesus was even born.
Try and get your head round that!
MORE GOLDS THAN 174 COUNTRIES
Having moved on to 22, Phelps now has more gold medals than 174 countries who have sent competitors to Olympic Games over the years.
Just think about that for a second.
In terms of all-time summer Olympic golds, Phelps on 22 is now just one behind the entire total of giant nations such as Brazil and South Africa when it comes to success in the pool.
Both of those countries have 23 swimming golds each in Olympic history.
GOLD AT FOUR STRAIGHT GAMES
Much is made of Phelps' remarkable medal haul and his constant domination of his own sport, not to mention the numerous world records he's broken.
But what must be applauded is the swimmer's longevity.
To win gold so regularly when it matters most is an impressive feat and is a credit to his regular but brutal training regime.
MEDLEY DOMINATION
Phelps thrives on the 200m individual medley and his latest gold maintained his perfect record in one of swimming's toughest disciplines.
Phelps has won the medley in each of the past four Games and hasn't lost in the event at the highest level since his debut in Athens in 2004.
It has seen Phelps equal his countryman Carl Lewis in winning the same individual event at four consecutive Olympics.
MORE GOLD TO COME?
More glory for Phelps could be on the way if he is able to win his fourth successive gold in the 100m butterfly.
The American qualified for Saturday's final shortly after his 200m medley victory.
ENJOY HIM WHILE YOU CAN
Phelps is now 31 and has indicated the Rio Games could well be his last Olympics.
If that's the case, there's no doubt he's going out on a high!
BUT COULD TOKYO BE A TARGET?
After destroying the field in numerous events at London 2012, Phelps seemed to turn his back on swimming.
But he came back for Rio and although he's said he'll call it quits after Rio, you couldn't totally rule out him being in the pool in Tokyo in 2020.
And, if he was there, you'd be a brave man or woman to bet against him winning gold.
