STORY: West Ham took the lead in the 62nd minute when Said Benrahma converted a penalty after a VAR review confirmed a handball by the Italian side's captain Cristiano Biraghi, who had been a thorn in West Ham's side with his runs down the flank.
Fiorentina immediately stepped up the pace after going behind and were rewarded five minutes later when Giacomo Bonaventura controlled the ball with two defenders on him and sent an angled shot past West Ham keeper Alphonse Areola.
Both sides struggled to create much in a nervy opening half with Fiorentina controlling possession but lacking a cutting edge in the final third, while West Ham had long spells without the ball.
When the referee blew the final whistle, the West Ham players raced to the corner to celebrate in front of their fans who reveled in the team's first win in a European final since they lifted the Cup Winners' Cup in 1965.
The supporters of both teams made their presence felt in a noisy atmosphere, though the referee was forced to stop play midway through the opening half after West Ham fans threw cups at Fiorentina's Biraghi, hitting the defender on the head and drawing blood.
UEFA had allotted only 5,780 tickets to each club, leaving legions of supporters unable to attend the match at Slavia Prague's stadium with a capacity set at 18,000 for the final.
Many thousands of West Ham supporters instead watched the match in bars and fan zones aground the city. Earlier in the day, Czech police said they had detained 16 Fiorentina supporters after they attacked West Ham fans in a local bar and a police officer.