Linkin Park Underground (often referred to as The LPU) is the official fan club of the nu-metal band Linkin Park. Users can share recent updates and album news about Linkin Park in the forum provided on its website. Members also have an email address @linkinpark.com, through which members can get new news about the band before the public. Giveaways also include small items such as Linkin Park pre-sale products such as albums, clothing, and some books.

Linkin Park Underground was founded in 2001 by Linkin Park and Jessica Bardas. LPU serves as a platform for Linkin Park fans to share their passion with the band. It has new membership gift packages every year. In the first year, LPU reissued the Hybrid Theory EP as a gift to registered users. The first 500 LPU members also received an EP album signed by the band as a thank you. Before January 31, 2005, LPU had a forum for fans to trade LP merchandise. However, this forum was closed due to disputes with some members.

In September 2005, a similar fan club called Fort Minor Militia was formed for Mike Shinoda's Hip-Hop group Fort Minor. The first 100 members received a copy of Fort Minor's new album The Rising Tied, including a DVD and other merchandise, as well as an autograph from Shinoda. Since then, LPU has gone through several major website changes and is now in its eighth year. At the same time, LPU has released eight Underground CDs, the latest of which is LP Underground V8.0.