Isaac Guerendo (gwy-REN-doh; born June 28, 2000) is an American professional football running back and kickoff returner for the San Francisco 49ers of the National Football League (NFL). He played college football for the Wisconsin Badgers and Louisville Cardinals.

Guerendo was born in Clayton, Indiana and attended Avon High School in Avon, Indiana. As a junior, he hauled in 19 receptions for 596 yards and six touchdowns. Guerendo had a breakout senior season, bringing in 54 receptions for 1,258 yards and 16 touchdowns. As a senior, he was named the Indianapolis Star's Mister Football for wide receivers.

Coming out of high school, Guerendo decided to commit to play college football for the Wisconsin Badgers.

In Guerendo's first season in 2019, he carried the ball once for one yard, while also making one catch for three yards, and returning one kickoff for 49 yards.

During the COVID shortened 2020 season, Guerendo carried the ball 11 times for 36 yards.

In Week 2 of the 2021 season, Guerendo recorded his first career touchdown on an 82-yard run versus Eastern Michigan. He finished the season with 160 yards and a touchdown of 23 carries, while also racking up two receptions for six yards.

In 2022, Guerendo rushed for 385 yards and five touchdowns on 64 carries, while also notching 17 receptions for 115 yards and a touchdown. At the end of the season, Guerendo decided to enter the NCAA transfer portal.

Guerendo finished his Wisconsin Badger career playing in 20 games carrying the ball 99 times for 582 yards and six touchdowns, while also notching 20 receptions for 124 yards and a touchdown. He graduated from Wisconsin in December 2022 with a bachelor's degree in personal finance.