The move is completed just in time for Friday's Premier League opener away to champions Arsenal, with Coventry back in the top flight for the first time in 25 years following last season's Championship title success.
Awoniyi spent the last four seasons in the Premier League with Forest, scoring 21 league goals in 90 appearances and 23 in 103 across all competitions. His career began at Liverpool, where loan spells took him to FSV Frankfurt, NEC Nijmegen, Mouscron and KAA Gent before he moved into German football with Mainz 05 on loan for the 2019-20 season and then 1. FC Union Berlin the following year.
That form at Union Berlin persuaded the club to sign him permanently in the summer of 2021, and Awoniyi went on to enjoy his best goalscoring season there, netting 20 times including four in the UEFA Conference League. Those performances caught the eye of Nottingham Forest, who broke their transfer record to sign him in 2022.
The Nigerian scored 11 goals in his first campaign at the City Ground, helping Forest avoid relegation in their first season back in the top flight and reach the Carabao Cup semi-finals. He was also part of the squad that finished seventh and qualified for Europe in 2024-25, before opportunities became more limited last season, with Awoniyi starting only three of his 17 Premier League appearances.
Awoniyi becomes Frank Lampard's sixth signing of the summer, following Gus Hamer, Carl Rushworth, Loum Tchaouna, Aurèle Amenda and Caleb Yirenkyi through the door at the CBS Arena. He was given a guard of honour by Forest's squad during their preseason friendly against Brest as he said his farewells to the City Ground.
"I'm very happy to complete my move to Coventry City," Awoniyi said. "I am very excited about this season, and I can't wait to get started.
"I'm really looking forward to working with my new teammates, I have seen how amazing they have been last season, coming up from the Championship, they were incredible and now I am just excited to join them and get started for the new season."
Awoniyi has also been capped ten times by Nigeria, scoring twice for his country.