Lockdown (2008) was a professional wrestling pay-per-view (PPV) event produced by the Total Nonstop Action Wrestling (TNA) promotion, which took place on April 13, 2008 at the Tsongas Arena in Lowell, Massachusetts. It was the fourth under the Lockdown chronology and fourth event in the 2008 TNA PPV schedule. Eight professional wrestling matches, two of which for championships, were featured on the card. In the tradition of Lockdown events, every match took place inside a six sided steel structure known as the Six Sides of Steel.

The main event was for the TNA World Heavyweight Championship between then-champion Kurt Angle and Samoa Joe, with the added stipulation if Joe lost he would retire from professional wrestling. Joe won the encounter, thus winning the TNA World Heavyweight Championship for the first time. Also held on the card was the 2008 Lethal Lockdown match between Team Cage and Team Tomko. Team Cage of Christian Cage (captain), Matt Morgan, Kevin Nash, Rhino, and Sting defeated Tomko (captain), A.J. Styles, James Storm, and Team 3D (Brother Devon and Brother Ray) of Team Tomko in the contest. Two featured bouts were scheduled on the undercard. The first was an Intergender Tag Team match pitting the team of Robert Roode and Payton Banks against the team of Booker T and Sharmell. Booker T and Sharmell were the victors in the match. The TNA X Division Championship was defended in the 2008 TNA Xscape match by Jay Lethal against Consequences Creed, Curry Man, Johnny Devine, Shark Boy, and Sonjay Dutt. Lethal won the competition to retain the championship.