Fortnite was developed by Epic Games, a video game company led by CEO Tim Sweeney. The concept for Fortnite originated in 2011 when Epic Games began exploring new game ideas, and the early development involved building forts and defending against zombies. Fortnite was built using the Unreal Engine and was initially released with a focus on cooperative gameplay before its massive success came with the launch of the free-to-play Battle Royale mode in September 2017.
Tim Sweeney, founder and CEO of Epic Games, is often credited for creating the company behind Fortnite, though he attributes the game's development to his team of developers. Epic Games had previously made titles like Unreal Tournament and Gears of War before Fortnite became a global phenomenon.
In summary, Fortnite was made by Epic Games under Tim Sweeney's leadership, with its development starting in 2011 and rising to prominence with its Battle Royale mode in 2017.