The Lions have been relegated from Super Rugby by the Saru general council after the Johannesburg-based team finished last in this year's competition.
A statement released by Saru on Thursday said the top four teams in the South African conference this year, the Stormers, Bulls, Sharks and Cheetahs, would join the Southern Kings in the 2013 tournament.
It said the Kings, based in the Eastern Cape, would be guaranteed only one year in the competition that also includes New Zealand and Australian franchises.
They will play a two-legged promotion/relegation match against the team who finish last in the South African Conference next year. – Reuters.