The Gunners were ahead inside five minutes thanks to Pierre-Emerick Aubameyang's close-range finish, which he followed up with an assist for Ainsley Maitland-Nile's goal 10 minutes later.
Aubameyang added a third for the home side in the second half to complete the comeback, having trailed 3-1 from the first leg seven days ago.
Relive how the 90 minutes of action unfolded with Sports Mole's live text coverage below.
STARTING XI: Cech; Mustafi, Koscielny, Monreal; Maitland-Niles, Ramsey, Xhaka, Kolasinac; Ozil; Lacazette, Aubameyang
SUBS: Leno, Mkhitaryan, Torreira, Iwobi, Suarez, Guendouzi, Nketiah
STARTING XI: Koubek; Traore, Da Silva, Mexer, Bensebaini; Sarr, Andre, Grenier, Bourigeaud; Ben Arfa, Niang
SUBS: Badiashile, Zeffane, Doumbia, Gelin, Siliki, Del Castillo, Hunou
Chelsea bang in 5. Arsenal are already 2 up. English clubs are smashing it this season. 👏👏— Gary Lineker (@GaryLineker) March 14, 2019
ARSENAL SUBS: Leno, Mkhitaryan, Torreira, Iwobi, Suarez, Guendouzi, Nketiah
RENNES SUBS: Badiashile, Zeffane, Doumbia, Gelin, Siliki, Del Castillo, Hunou
14 - Pierre-Emerick Aubameyang has been directly involved in 14 goals in his last 13 appearances at the Emirates (10 goals, 4 assists). Flying. pic.twitter.com/IjffOOIQcq— OptaJoe (@OptaJoe) March 14, 2019
In the middle of all that, Rennes brought on Hunou for Grenier.