2K Games and Valve have announced an agreement this week that has brought four hit PC strategy titles from 2K's roster to Steam. The four titles include Sid Meier's Civilization IV, Sid Meier's Civilization III, Sid Meier's Pirates!, and Shattered Union.

All four titles are now available for purchase on Steam, Civ IV at $49.95 and the remaining three for $29.95. Other 2K Games titles are possible future additions to Steam as well, however at this time no details have been released.