Louis M. "Lou" Groen (born August 8, 1917 – died May 30, 2011) was an entrepenuer, and businessman of Cincinnati, Ohio, where he was born and raised, and also a lifelong resident. Groen invented the Filet-O-Fish sandwich in 1962. He invented the sandwich at his floundering McDonald's restaurant to satisfy his customers. At the time, most of his customers were Roman Catholic, who had to abstain from eating meat on Friday. His invention (the fish sandwich), served with cheese and tartar sauce, is now served at McDonald's restaurants throughout the world.