The 1967 Oak Lawn tornado outbreak was a destructive tornado outbreak and severe weather event that occurred on April 21, 1967, across the central Midwest, in particular the towns of Belvidere and Oak Lawn, Illinois, United States. Locally known as 'Black Friday,' it was the largest tornado outbreak of 1967 and one of the most notable to ever occur in the Chicago metropolitan area. The outbreak produced numerous and significant (F2+) tornadoes, with ten of them in Illinois alone. Included was one of just six documented violent (F4/F5) tornadoes in the Chicago metropolitan area since the area was first settled.

Evergreen Park is a village in Cook County, Illinois, United States. In 2020, the population was 19,943.