Double Olympic champion one of three French judoka to triumph as the season-opening World Judo Tour event concludes in Qatar
Riner was never troubled by his Russian opponent, the world number three, and looked back to his best after a surprise 2020 season which included two defeats.
Tasoev, shorter in stature than Riner, struggled to properly get a grip on his French opponent, and received three shido penalties which awarded the title to Riner.
It was France's third gold medal of the day and fifth of the tournament.
Earlier, there was also French success in the women's half-heavyweight (-78 kg) and heavyweight (+78 kg) categories.
In the under-78 kg class, world champion Madeleine Malonga defeated Hamada Shori of Japan in a repeat of the 2019 world final.
Malonga scored an early waza-ari 23 seconds into the bout, and that point was enough for her to see off Hamada.
Romane Dicko scored an impressive victory in the heavyweight category, coming through her pool by defeating world number one and three-time Olympic medallist Idalys Ortiz before seeing off world number seven Kayra Sayit of Turkey in the semi-finals and world number four Iryna Kindzerska of Azerbaijan in the final.
Each of Dicko's four victories in the competition came by ippon.
In the men's -90 kg, Dutch world champion Noel van 't End defeated Beka Gvinishvili of Georgia in the final.
van 't End scored a waza-ari 1:39 into the bout and eventually took his opponent down for an ippon score to end the bout.
Gvinishvili's teammate Varlam Liparteliani, the Rio silver medallist at -90 kg, clinched -100 kg gold in a tense final.
A drop Seoi move awarded a waza-ari to Liparteliani, the only score of that bout.