Favourite Noah Lyles posted 19.86, with the American 0.09s ahead of Alex Quinonez (Ecuador).
Gemili ran a season’s best 20.03 to finish first in the opening semi-final, with reigning world champion Ramil Guliyev of Turkey qualifying in second.
Gemili’s time was matched by China’s Zhenye Xie, while Canadian duo Andre De Grasse and Aarom Brown, as well as Trinidad's Kyle Greaux, also made the final.
There was disappointment for GB’s Hughes however, who finished third in his heat behind De Grasse and Greaux – with his 20.30 not quick enough to qualify as one of the next two fastest sprinters.
The final will take place on Tuesday night, with 22-year-old Lyles expected to take his first world gold having run the fourth-fastest ever 200m in 19.50 earlier this year.
Warholm caps perfect season with world 400m hurdles gold
Norway's Karsten Warholm completed a perfect season by blazing to world championship gold in the 400m hurdles on Monday while Abderrahman Samba finally gave the hosts something to cheer claiming a bronze and Qatar's first medal.
The silky smooth Warholm, the second fastest ever over the distance, did not come close to Kevin Young's world record that many thought might fall but his time of 47.42 seconds was good enough to ensure a successful defence of his title.
The Norwegian's great rival American Rai Benjamin took silver in 47.66 while Samba delighted the home fans by claiming the bronze.
Karsten Warholm of Norway celebrates winning gold in the Men's 400 metres hurdles final during day four of 17th IAAF World Athletics Championships Doha 2019
Image credit: Getty Images
For the final event of the night the athletes were introduced with a spectacular light show worthy of a race expected to produce fireworks.
With three of the four quickest men ever in the event on the starting blocks, the 400m hurdles was circled early as the marquee event of the world championships.
The race was expected to come down to a duel between the Norwegian and the American who pushed each other to career best times in Zurich in August and it unfolded as predicted.
There has been precious little for Qataris to cheer at Khalifa Stadium but the biggest crowd of the championships were on their feet when Samba, the third fastest man of all time, stepped onto the track and rewarded them with a bronze.
Russian Lasitskene first woman to clinch three world high jump titles
Maria Lasitskene became the first woman to win a third world high jump title, gracefully clearing 2.04 metres on Monday to bring Russia's neutral athletes a second gold in two days.
Dominating the competition from the start, the 26-year-old continued to raise the bar after having secured gold in an attempt to achieve a personal best of 2.08m.
Image credit: Getty Images
Although Lasitskene missed out on that mark with three failed attempts, she again demonstrated her absolute dominance of her discipline by clearing 2.04m at her first attempt.
Like the other Russians competing in Doha, Lasitskene was barred from celebrating her victory with a Russian flag and will not hear her country's anthem when she steps onto the podium.
Without her flag, Lasitskene ran down the track, waving and blowing kisses to the crowd, while Ukrainian silver medallist Yaroslava Mahuchikh and American bronze winner Vashti Cunningham brandished their countries' flags.
Edris retains 5,000 metres world title in thrilling finale
Ethiopia's Muktar Edris won a thrilling battle over the last 200 metres to retain his title in the 5,000 metres.
The 25-year-old, roared on by a noisy contingent of flag-waving Ethiopian fans in the crowd, outsprinted compatriot Selemon Barega to win in 12 minutes 58.85 seconds.
It was the first 5,000 world championship final since 2005 not to feature Britain's Mo Farah who has won the title three times.
Mo Ahmed took the bronze to win Canada's first-ever world championship medal over the distance.
Additional reporting from Reuters