Centrowitz, fourth in the London Games four years ago and twice a world championship medallist, timed 3min 50.00sec.
Algerian defending champion Taoufik Makhloufi added silver to second place in the 800m, in 3:50.11, while New Zealand's Nicholas Willis claimed bronze (3:50.24).
"There's nothing like it. It doesn't compare to anything else I've won in my life," said Centrowitz.
The last American to win the 1500m in the Olympics was Mel Sheppard in the 1908 London Games, and Centrowitz was left shell-shocked by his performance.
"Seb said: welcome to the club!
"Everything leading up to it, during and after has been surreal. "I saw my dad on my victory lap and I yelled 'are you kidding me?!' and he yelled back 'are you effing kidding me?!' and it kept going back and forth. I don't think any of us believed it."
"The Olympics are the pinnacle of track and field. This is the best that it gets. I've been joking since I got this medal that I don't have to do anything else in my career!
"On the best day I thought I could have got silver. Coming away with gold is unbelievable," said Centrowitz.
The American and Spain's David Bustos set a slow early pace, Makhloufi boxed in the chasing pack with Kenyan favourite Asbel Kiprop.
The opening two laps were timed at a relatively pedestrian 66 and 69.7sec respectively.
Kiprop decided to move, and motored up through the field as the pace accelerated.
Morocco's reigning world and Olympic bronze medallist Abalaati Iguider and Djibouti' Aynaleh Souleiman pushed Centrowitz through the bell for the last lap, with all eyes on Kiprop and Makhloufi.
As expected, the Kenyan made his move with 300 metres to run, the Algerian sweeping in on his coat-tails.
"After the first 800 metres when no one came around me, I thought ok no one's going around me now," he said.
His face gritted in determination, the 26-year-old American, coached by Alberto Salazar, held on for a shock victory, timing 50.62sec for the last lap.
Kiprop was reeled in down the straight by Souleiman and Willis and eventually finished sixth, 0.87 off Centrowitz's pace.
Willis, who won silver at the 2008 Games in Beijing, said the moment was not as "joyous" as he thought it would be.
"It doesn't have that euphoria I was expecting - maybe because the race was so slow, we didn't expend that much energy, it came a bit too easy."
Willis added: "After 2008, I had three different surgeries, it took me four years to get back in to form. A lot of people write you off in your 30s. This is for all the 30-year olds."
Willis also didn't count himself on whether he could still compete at a fifth Olympics:
"What do you think? I think I can do five.
Disclaimer: No Business Standard Journalist was involved in creation of this content
You’ve reached your limit of {{free_limit}} free articles this month.
Subscribe now for unlimited access.
Already subscribed? Log in
Subscribe to read the full story →
Smart Quarterly
₹900
3 Months
₹300/Month
Smart Essential
₹2,700
1 Year
₹225/Month
Super Saver
₹3,900
2 Years
₹162/Month
Renews automatically, cancel anytime
Here’s what’s included in our digital subscription plans
Exclusive premium stories online
Over 30 premium stories daily, handpicked by our editors


Complimentary Access to The New York Times
News, Games, Cooking, Audio, Wirecutter & The Athletic
Business Standard Epaper
Digital replica of our daily newspaper — with options to read, save, and share


Curated Newsletters
Insights on markets, finance, politics, tech, and more delivered to your inbox
Market Analysis & Investment Insights
In-depth market analysis & insights with access to The Smart Investor


Archives
Repository of articles and publications dating back to 1997
Ad-free Reading
Uninterrupted reading experience with no advertisements


Seamless Access Across All Devices
Access Business Standard across devices — mobile, tablet, or PC, via web or app
