Hart will be joined by Foo Fighters as the musical guest, back for the seventh time on the series.
As Kevin Hart famously once said, "It's about to go down!"
Saturday Night Live airs Saturday at 11:30 p.m. ET/8:30 p.m. PT on NBC. This will be Ronan's hosting debut on SNL as well as a great opportunity for her to plug her acclaimed new movie Lady Bird.
Those SNL episodes will round out December's three-week run of new shows. Franco is a favorite guest at SNL, so much that Lorne Michaels even let him shoot the documentary Saturday Night from behind the scenes of the John Malkovich-hosted episode in 2008.
Meanwhile, U2 will be the musical guest that night.
The hosts will have some formidable musical accompaniment. too.
SNL ends 2017 with a bang on December 16 when comedian Kevin Hart hosts the show for the third time, days ahead of the release of his latest film, Jumanji: Welcome to the Jungle.