The 2005 Slammiversary was a professional wrestling pay-per-view (PPV) event produced by the Total Nonstop Action Wrestling (TNA) promotion, which took place on June 19, 2005 at the TNA Impact! Zone in Orlando, Florida. It was the first event under the Slammiversary chronology and the sixth event in the 2005 TNA PPV schedule. Nine professional wrestling matches, three of which featured championships, and one pre-show match were featured on the event's card. The event commemorated TNA's third anniversary, after forming on June 19, 2002.

The main event was the 2005 King of the Mountain match for the NWA World Heavyweight Championship, in which then-champion A.J. Styles defended the title against Abyss, Monty Brown, Sean Waltman, and Raven. Raven won the match and the NWA World Heavyweight Championship. The TNA X Division Championship was defended in a Three Way Elimination match by Christopher Daniels against Chris Sabin and Michael Shane. Daniels retained the championship in the encounter. On the undercard, America's Most Wanted (Chris Harris and James Storm) defeated the 3Live Kru (B.G. James and Konnan) in a tag team match. The debut of Samoa Joe was also promoted for the card. Joe defeated Sonjay Dutt in his first match for the company during the show.

The event is marked for the second-ever King of the Mountain match and the debut of Samoa Joe. Jason Clevett of the professional wrestling section of the Canadian Online Explorer rated the event a 7 out of 10, higher than the 2006 event's ranking of 6.5 out of 10 by Chris Sokol.