The deal ends months of uncertainty over the future of the Formula One team that is likely to persist with its estranged partner, Renault.
Red Bull have an engine deal in place for next season after months of uncertainty, team principal Christian Horner said on Friday.
"We've entered the world championship, we've signed a contract for an engine, but I can't tell you what it'll be or called at the moment," Horner said at the season-ending Abu Dhabi Grand Prix.
The engine is almost sure to be a Renault one, although likely to be branded with a different name and possibly with design input from a third party or Red Bull's own technical input.
Renault is Red Bull's current partner, but the relationship has strained to breaking point due to the V6 turbo hybrid unit's lack of performance. Despite the strained relationship, their contract, not due to expire until the end of 2016, is understood to remain in place.
The two shared a very successful partnership when they won four consecutive titles from 2010 to 2013.
Renault is still thinking about their future in the sport, and a possible takeover of the Lotus team, with a decision expected imminently.
Mercedes have already refused to supply Red Bull, and Ferrari are willing only to make available year-old units to sister team Toro Rosso and McLaren have a veto over Honda supplying anyone else next season. Apart from those three, Renault is the only remaining option.
Red Bull announced previously they had entered next year's championship and have recently been announcing a string of sponsorship renewals.