Tola clocked an Olympic record of 2hr 06min 26sec for victory, finishing 21 seconds ahead of Belgium's Bashir Abdi, whose silver marked an upgrade from his bronze garnered at the Covid-hit Tokyo Games three years ago.
Kenya's Benson Kipruto, winner of Tokyo, Boston and Chicago marathons in recent years, rounded out the podium, a further 13sec adrift.
"Thank you, Paris!" said Tola, the 2016 Olympic 10,000m bronze medallist who will be 33 on Sunday.
"I'm happy today, I was 2022 world champion and now I'm Olympic champion.
"It's the greatest day in my life. This was my goal."
Tola, a late call-up to replace injury-hit Sisay Lemma, won gold at the 2022 world championships in Eugene.
More recently he finished third at last year's London Marathon and won the New York City Marathon in a course record of 2:04.58.
"I was the reserve in the Ethiopian team, but when Sisay had injuries, then I had a chance to represent him," Tola said.
"I was fully prepared and knew I could fulfil my dream. This is the Olympics and it is not easy to win the Olympic Games, not at all. I am very proud, very happy."
No three-peat for Kipchoge
Former world record holder Kipchoge won golds in the 2016 Rio Games and in Tokyo in 2021, but the 39-year-old Kenyan pulled up late in the race with back pain.
He dropped out just after the 30km mark, at which point he was 71st, more than eight minutes off the pace.
It put an end to his ambitious attempt at a third consecutive win.
In scenes witnessed by an AFP reporter in the crowd, Kipchoge turned to fans and handed over his shoes, bib and socks to supporters, receiving a rapturous reception.
"Today was a tough day at the office," said Kipchoge. "It's like boxing. You can go to a training camp for five months and be knocked out in two seconds. But life will continue.
"This is my worst marathon. I have never done a DNF (did not finish). Like a boxer, I have been knocked down, I have won, I have come second, eighth, 10th, fifth – now I did not finish. That's life."
Tola's teammate Kenenisa Bekele, who won three Olympic and five world golds over 5000m and 10,000m before turning to the marathon, finished 39th in 2:12.24.
"It is fantastic that Ethiopia won the race. Tola is very strong, and I am happy for him," said the 42-year-old Bekele.
"People have been talking about me and Kipchoge, but you see it was the young generation today. These guys are stronger than us.
"These days there are many younger and stronger athletes, so it was tough to challenge them."
The 42km-long marathon course headed out of central Paris on a loop to Versailles, mimicking a key moment from the French Revolution: the Women's March on Versailles, on 5 October 1789 which led to French King Louis XVI finally agreeing to ratify the Universal Declaration of the Rights of Man and Citizens.
The route included a 436m climb and 438m descent. The maximum gradient on the route was 13.5 percent. "If you are not really fit for this course, then it will be very rough," said Bekele.
Silver medallist Abdi added: "The weather was hot, (the terrain featured) a lot of ups and downs. Actually, I expected going uphill would be most challenging, but I found going downhill most difficult.
"It was very steep and you don't have control of your body. That was very scary, especially after 29km, we had almost 2km of running downhill and it was just going more down and down, and I was really afraid of falling.
"This is the hardest marathon course I've ever run."
