One-lap specialist Norman clocks personal best to edge out his fellow American prospect, as Elaine Thompson returned to winning ways.
They might be old roommates and good friends, but Michael Norman and Noah Lyles were desperate to beat each other in the Rome Diamond League 200m.
And it was Norman who came out on top, powering off the bend to establish a lead he would just about retain to the line.
The California native said recently that the 400m was his priority this season, but he might be tempted to rethink that after winning in a new personal best of 19.70s.
Lyles was the fastest man in the world last year over 200m with 19.65s, but he could not quite catch his fellow American and had to settle for second in 19.72s.
Alex Quinones was a distant third ahead of world champion Ramil Guliyev.
Lyles and Norman are both 21 years old and have already marked themselves out as potential all-time greats.
The pair actually roomed together at the 2016 World U20 Championships in Poland where Lyles took the 100m and Norman the 200m before they teamed up for gold in the 4x100m relay.
Both men are both doubling up in individual sprint events over the course of the 2019 season.
Lyles won last month's Shanghai Diamond League over 100m, beating 2018 world leader Christian Coleman in a new personal best of 9.86s.
But he said again on Wednesday (5th June) that the 200m - the event in which he took Youth Olympic gold at Nanjing 2014 - was his focus ahead of the World Championships in Doha starting in September.
"Right now my goal is to run the 200m. That's my bread-and-butter event." - Noah Lyles in press conference on the eve of the Rome Diamond League.
But he could not beat Norman, the younger of the two by less than five months, in Rome's Stadio Olimpico.
Norman only turned professional in May, and tonight's heroics saw him further enhance the reputation he created at college where he broke the world indoor 400m record.
His coach, 1992 Olympic gold medallist Quincy Watts, believes he could be the greatest one-lap runner in history.
"I've seen Butch Reynolds, Steve Lewis, Michael (Johnson) and Wayde (van Niekerk). I have never seen anyone like him. He has the potential speedwise to be faster than them all." - Quincy Watts to Reuters on Michael Norman
Jamaica's double Olympic champion finished behind the Briton over 200m in Stockholm last week, but she ran a world-leading 10.89s to exact revenge in the short sprint.
Shanghai winner Aleia Hobbs was third ahead of double world silver medallist Marie-Josee Ta Lou.
Germany's Malaika Mihambo sprung a surprise in the women's long jump, taking victory with a new personal best of 7.07m.
Double triple jump Olympic champion Caterine Ibarguen was second with 6.87m ahead of London 2012 long jump gold medallist Brittney Reese - making her first Diamond League appearance since 2017 - on 6.76m.
No fewer than seven women attempted 4.76m in the pole vault, but only one was successful.
Konrad Bukowiecki of Poland set a personal best to win the men's shot, throwing 21.97m in round five for a new meeting record.
Doha Diamond League victor Nijel Amos had to settle for second in Rome as Donovan Brazier of the United States pipped him on the line.
Brazier's time of 1:43.63 was the fastest in the world of year ahead of Botswana's London 2012 silver medallist.
There was another close finish in the 5,000m as Telahun Haile Bekele ran down fellow Ethiopian Selemon Barega in the closing strides to win in a world-leading 12:52.98 which was also a new personal best.
Ethiopia also took the women's 1500m as former world champion and Rio 2016 runner-up Genzebe Dibaba came home ahead of Britain's Laura Muir.
Dibaba clocked 3:56.28, another best time in 2019.
China's Lyu Huihui won the women's javelin with a throw of 66.47m.
On her first Diamond League appearance for two years after taking 2018 off to have a baby, double Olympic javelin champion Barbora Spotakova was seventh with 61.51m.