Richard Rusczyk
From AoPSWiki
Richard Rusczyk is the founder of the Art of Problem Solving website and co-writer with Sandor Lehosczky of the original Art of Problem Solving books. He is also a co-founder with Sandor Lehosczky and Sam Vandervelde of the Mandlebrot Competition. A picture of him can be found here.
His username on AoPS is rrusczyk