Foss is a former world time trial champion and has been with Jumbo-Visma for the past three years.
He has signed a three-year deal.
"When I was 14 years old and started cycling, Edvald Boasson Hagen and Team Sky (now Ineos) became my idols and my favourite team. After that Chris (Froome), Bradley (Wiggins) and Geraint (Thomas) inspired me as I dreamt of the Tour de France.
"All of this made the INEOS Grenadiers my dream team so this was a big factor in me signing, together with my belief that this team can help me further my career."
His best finish in a Grand Tour was ninth in the 2021 Giro d'Italia but he is yet to feature in the Tour de France.
Steve Cummings, Sport Director for Ineos Grenadiers, said: "Tobias is renowned for his time trialling ability, but with what he's achieved in the past he has also shown he can really climb too.
"He's achieved a range of very good results and we fully believe he has the versatility to play a key part in a GC team."
