Teen Mom (renamed Teen Mom OG, starting with the fifth season) is an American reality television series broadcast by MTV. It is the first spin-off of 16 and Pregnant, and it focuses on the lives of several young mothers as they navigate motherhood and strained family and romantic relationships. Its first run consists of four seasons originally aired between December 8, 2009, and October 9, 2012, while another four seasons have aired during its second run that began on March 23, 2015. Season 9 premiered on January 26, 2021.

The series originally focused on the lives of Maci Bookout (now McKinney), Catelynn Lowell (now Baltierra), Amber Portwood, and Farrah Abraham, who were featured on the first season of 16 and Pregnant. Are You the One? participant Cheyenne Floyd and television personality Bristol Palin joined in the second half of the seventh season replacing Abraham who departed from the show. However, Palin departed the show following an announcement on Instagram in April 2019. In August 2019, Mackenzie McKee from Teen Mom 3 joined the cast as a guest mom for the last few episodes of season eight. Mackenzie McKee officially became a main cast member on season 8b.

The show's success has allowed for the development of the spin-offs Teen Mom 2, Teen Mom 3, Teen Mom: Young and Pregnant, Teen Mom: Young Moms Club, Teen Mom: Family Reunion, and Teen Mom: Girls' Night In.

On May 22, 2022, the series was merged into Teen Mom 2, with cast members of each series transitioning to a combined series titled Teen Mom: The Next Chapter, which premiered on September 6, 2022.