Red Bull has confirmed that Max Verstappen will join the team with immediate effect, with Daniil Kvyat returning to Toro Rosso.
Kvyat endured a challenging Russian Grand Prix, twice making contact with Sebastian Vettel through the first sequence of corners before going on to finish a lowly 15th.
Verstappen will partner Daniel Ricciardo, while Kvyat will join Sainz Jr. at Toro Rosso, having raced for the team in 2014.
"Max has proven to be an outstanding young talent," said Red Bull boss Christian Horner.
"His performance at Toro Rosso has been impressive so far and we are pleased to give him the opportunity to drive for Red Bull Racing.
"We are in the unique position to have all four drivers across Red Bull Racing and Toro Rosso under long term contracts with Red Bull, so we have the flexibility to move them between the two teams.
"Dany will be able to continue his development at Toro Rosso, in a team that he is familiar with, giving him the chance to regain his form and show his potential."
Verstappen thanked Toro Rosso after his 23-race stint with the team came to an end.
"I can’t thank all the people at Toro Rosso enough for all their hard work," he said.
"Everyone back at the factory in Faenza, and Franz Tost in particular, have made an amazing contribution to get me this far in my career. We’ve had an amazing time together
"The next step in my relatively short career so far, is an amazing opportunity. I really want to thank Red Bull Racing and Dr. Helmut Marko for the confidence they have in me.
"I’ll have the chance to learn a lot from the top team that is Red Bull Racing. I’m also looking forward to work with an experienced and proven team mate like Daniel."