Warholm went out fast and briefly looked capable of challenging Kevin Young's 1992 world record of 46.78 seconds, but faded on the last bend and won in 47.42. Warholm celebrated his victory lap in a horned Viking-style helmet.
Rai Benjamin of the United States took silver in 47.66, while Abderrahman Samba delighted the Qataris in the sparse crowd with bronze in 48.03.
Mariya Lasistkene won her third straight world high jump title and Russia's second gold medal of the championships.
Lasitskene was officially competing as a neutral athlete because Russia's track and field federation has been suspended since 2015 over widespread doping. The Russian anthem won't play during her medal ceremony. Both she and silver medalist Yaroslava Mahuchikh of Ukraine cleared 2.04 meters but Lasitskene prevailed because Mahuchikh had failed six attempts at lower heights earlier in the competition.
Vashti Cunningham won bronze for the U.S. on 2 meters.
Lasistkene was visibly frustrated when Mahuchikh started celebrating with the Ukrainian flag in front of her fans after securing silver but before the competition had finished. Mahuchikh withdrew at 2.04, having already jumped far higher than her personal best, and Lasistkene missed three attempts at 2.08, a height one centimeter short of the world record.
Sweden's Daniel Stahl went one better than his 2017 silver medal with gold in the discus, throwing 67.59 meters. Fedrick Dacres of Jamaica was second and Lukas Weisshaidinger of Austria third.
Kenya's Beatrice Chepkoech stayed on course and won the women's steeplechase in a breeze, while Uganda's Halimah Nakaayi used a late kick to take the 800-meter race being run without Caster Semenya.
Chepkoech finished the steeplechase in a world-championship record time of 8 minutes, 57.84 seconds to beat the American defending champion, Emma Coburn, by more than 4.5 seconds.
At worlds two years ago in London, Chepkoech lost ground that she couldn't make up when she inexplicably missed the turn for the water jump on the inside of the track early in the race. Coburn led a 1-2 U.S. finish that night. She ran faster Monday on the track in Doha, but her time — a personal-best 9:02.35 — wasn't near close enough.
In the 800, Nakaayi finished in 1:58.04 to beat the American duo of Raevyn Rogers and Ajee Wilson.
The race was run without the defending champion, Semenya, who has refused to follow new IAAF rules requiring her to medically reduce her natural testosterone level. Semenya's winning time in 2017 was 1:55.16
Muktar Edris has defended his title in the men's 5,000-meter race at world championships — and this time it wasn't a surprise.
The Ethiopian, who upset Mo Farah in Farah's farewell to the event two years ago, used a late kick to beat countryman Selemon Barega to the finish.
Edris completed the 12 ½ laps in 12 minutes, 58.05 seconds and drew some of the biggest cheers of the meet so far. The crowds in Doha have been sparse, but the flag-waving contingent from Ethiopia has filled two full sections on nights their runners are going.
This race was considered wide open because two of the top at the distance, Yomif Kejelcha and Joshua Cheptegei, were not in the field to focus on the 10,000.
But Edris finished where he did at the last worlds — on top — and brought Ethiopia, which has the loudest fan contingent in Doha, its first gold medal of the championships.
The IAAF anthem played. The IAAF flag was raised. The fans in the sparse crowd even stood.
That's how Russian pole vaulter Anzhelika Sidorova was honored as a neutral athlete in her gold-medal ceremony.
Sidorova was granted neutral status after the IAAF, track's governing body, vetted her drug-testing record. She's allowed to compete here along with 29 of her Russian teammates. They're banned from displaying any national symbols.
After winning the event Sunday, Sidorova made her way around the track for a victory lap without a flag.
Blessing Okagbare was disqualified from the 200 meters for a second time.
Because of a mix-up by her nation's track federation, the Nigerian sprinter was initially disqualified after she didn't show up for the 100-meter races that she never intended to run. Only after an appeal and a long wait did Blessing find out she was back in.
But when she got to the race she was disqualified for stepping outside of her lane.
Nigeria's track federation had entered both her and Divine Oduduru in the 100-meter races, even though neither intended to compete at that distance. When they didn't show up, IAAF rules called for them to be disqualified from the rest of the meet, including their main events, the 200, and the 4x100 relays.
But after learning more about the mix-up, an IAAF appeals panel reinstated them.
Oduduru advanced out of the first round in the men's race.
Netherlands sprinter Dafne Schippers won't defend her title in the 200 meters at the world championships because of an injury.
Schippers strained an adductor muscle in the semifinal of the 100 on Sunday and didn't race in the final. It wasn't any better after warming up Monday and she didn't start her first-round heat of the 200.
She won the event in 2015 and '17. The 27-year-old also earned an Olympic silver medal in the 200 at the 2016 Rio de Janeiro Games.
Schippers remains questionable for the 4x100 relay.
Distance-running great Haile Gebrselassie says it was wrong to hold the track and field world championships in Qatar and marathon runners could have died from the heat.
Gebrselassie tells The Associated Press "it was a mistake to conduct the championship in such hot weather in Doha, especially the marathon race. As someone who has been in the sport for many years, I've found it unacceptable."
The women's marathon Friday started at midnight to dodge the worst of the heat in Qatar but was still held in humidity that made it feel like 105 degrees (40 Celsius). Twenty-eight of the 68 women dropped out and one was briefly hospitalized.
Gebrselassie, a two-time Olympic champion who was also president of the Ethiopian Athletics Federation, says "God forbid, but people could have died running in such weather conditions."
Ajee Wilson of the United States will target gold in the 800 meters on the fourth day of the track world championships Friday, before Norway's Karsten Warholm tries to defend his 400 hurdles title.
Wilson is one of three U.S. women in the 800 final, but they will face tough opposition from Jamaica's Natoya Goule and Kenyan Eunice Sum.
South Africa's Caster Semenya isn't racing because she refuses demands from the IAAF to reduce her natural testosterone levels.
Warholm only made it to the semifinals at the 2016 Olympics, but since then he has racked up the 2017 world gold, 2018 European gold and this year's European indoor and Diamond League titles.
Also Monday, there are medals on offer in the finals of the men's 5,000, the women's 3,000 steeplechase, the men's discus and the women's high jump.
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