The Sweden international has enjoyed a hugely impressive two-and-a-half years at the Sky Blues, contributing 43 goals and 17 assists from 116 appearances in all competitions.
Coventry had hoped that the performances of Gyokeres would ultimately lead to promotion to the Premier League last season, but they fell short in losing to Luton Town in the Championship playoff final.
With just one year left on Gyokeres's contract, it soon became clear that the 25-year-old would be allowed to depart the Midlands outfit for the right price.
Although a number of English top-flight sides have been heavily linked with Gyokeres, Sporting recently emerged as the clear frontrunners for his signature.
Both teams have now acknowledged that a deal has been finalised, Coventry revealing that it is the biggest fee that they have ever received for one of their players.
While Coventry do not reveal that figure, with the deal also including add-ons, transfer expert Fabrizio Romano says that Sporting have shelled out a club-record €24m (£20.49m).
Speaking on the deal, Coventry chairman Doug King said: "After a long discussion, we have finally concluded a deal that is right for all parties concerned and confirm the transfer of Viktor Gyokeres to Sporting Lisbon.
"Viktor has made a huge impression in his time with us and leaves many great memories and we wish him every success with his new club.
"This is a record transfer fee for Coventry City but as is normal will be paid over an extended period, with Brighton & Hove Albion taking a meaningful percentage share."
Coventry have already signed a replacement for Gyokeres in the form of Everton forward Ellis Simms, who netted seven goals and provided two assists during 17 Championship outings on loan at Sunderland in 2022-23.
From Sporting's perspective, Gyokeres is in line to become first choice in attack with playmakers Pedro Goncalves and Francisco Trincao emerging as their top goalscorers last season.
Gyokeres has penned a five-year contract at Estadio Jose Alvalade.