When Muhammad Ali called himself "the greatest" most people agreed. If Michael Phelps now does the same, no-one can really disagree.
Phelps became the most decorated athlete in Olympic history on Tuesday night by winning two more medals and swelling his career haul to an astonishing 19.
And he isn't finished yet, with three more events to contest in the 2012 Games before he calls it a day.
His London campaign is not reaping anywhere near the golden harvest of eight titles he won in Beijing, signalling his days of invincibility are over.
But he is still doing OK.
He was pipped for gold in the 200m butterfly on Tuesday by a storming finish from South African Chad le Clos, but was back on the winner's podium later after anchoring the US to victory in the 200m freestyle relay.
That took the 27-year-old from Baltimore past the 18 medals won in the 1950s and 60s by Soviet gymnast Larisa Latynina, who is now 77 years old and reportedly enjoying the London Games as a spectator in almost complete anonymity.
Phelps is now the greatest Olympian by any measure.
* His 19 medals is the most of all, one ahead of Latynina with daylight third - the mere dozen collected by legendary Finnish runner Paavo Nurmi in the 1920s.
* His 15 gold medals far outstrips the nine won by Latynina, Nurmi and Americans Carl Lewis and Mark Spitz.
* His eight gold medals in Beijing snatched the record for most in a single Games from Spitz.
* He may yet become the first male swimmer ever to earn gold in the same event in three straight Olympics. He missed doing that already in the 400m medley and the 200m butterfly, but he could still pull it off in two more individual events.
The difficulty of that feat is evident from the heroic but unsuccessful attempts at "three-peats" by Australian distance greats Kieren Perkins and Grant Hackett.
Phelps has buried every other Olympian by sheer weight of statistics, and the weight of his sackful of gold, silver and bronze.
Australia's most decorated Olympian, Ian Thorpe, by comparison has five gold medals (10 fewer than Phelps so far) and nine in all (also 10 behind Phelps).
Thorpe lies equal 35th on the all-time list now headed by Phelps.
Many may still regard Muhammad Ali as the "greatest athlete ever".
Before mesmerising the world in the pro boxing ring, Ali won an Olympic gold medal, too - at Rome in 1960 - which he threw into the Ohio River after being refused service at a 'whites-only' restaurant.
He was presented with a replacement medal at the 1996 Olympics in Atlanta, where he lit the torch to start the Games.
When it comes to style and charisma, Phelps isn't in the same league as Ali (who is?)
He can't sting like a bee, either. But he can sure float like a butterflier.
PHELPS - THE GREATEST OLYMPIAN
Olympic medals:
19 - Michael Phelps (US)
18 - Larisa Latynina (USSR)
12 - Paavo Nurmi (Finland)
Olympic gold medals:
15 - Michael Phelps (US)
9 - Larisa Latynina (USSR0
Paavo Nurmo (Finland)
Mark Spitz (US)
Carl Lewis (US)
Gold medals at a single Games:
8 - Michael Phelps (US)
7 - Mark Spitz (US)
Most Olympic medals for Australia:
9 - Ian Thorpe
8 - Dawn Fraser, Leisel Jones, Petria Thomas, Susie O'Neill
7 - Grant Hackett, Shirley Strickland
NZN