WrestleMania 21 was the twenty-first annual WrestleMania professional wrestling pay-per-view produced by World Wrestling Entertainment. It took place on April 3, 2005 at the Staples Center in Los Angeles, California. The event was the first WrestleMania at the Staples Center, but the fifth to take place in the Southern California metropolitan area (following WrestleMania 2, WrestleMania VII, WrestleMania XII and WrestleMania 2000). WWE claimed that tickets were sold out in less than one minute for this event, which would be a record for the fastest selling WrestleMania and WWE event ever and the fastest ticket sell-out in the Staples Center's history. The event drew a Staples Center record attendance of 20,193 people from 14 countries and 48 states and grossed more than $2.1 million USD in ticket sales, making it the highest grossing WWE event ever at the Staples Center, and the highest grossing of the five WrestleManias held in California. In addition to those in attendance, WrestleMania 21 was seen by millions of fans in more than 90 countries.

• WrestleMania 21 marked the first time the WWE Championship and the World Heavyweight Championship both changed hands on the same night in standard singles matches and at a WrestleMania.
• This event marked the fourth time at a WrestleMania that Triple H was played to the ring by a live band. At WrestleMania XIV by Chris Warren and The DX Band. At WrestleMania X-Seven by Motörhead, and at WrestleMania X8 by Drowning Pool.

Steve Austin celebrating with the crowd

• This would be Eddie Guerrero's final WrestleMania match before his untimely passing on November 13, 2005.
• This is the third WrestleMania to use Arabic numerals instead of Roman numerals (the previous two being WrestleMania 2 and WrestleMania 13).
• During the Money in the Bank Ladder match, Tyson Tomko helped Christian up the ladder using his head and back. At WrestleMania X-Seven during the TLC II match, Rhyno helped Christian up the ladder in a similar manner.
• Celebrity guests in attendance for WrestleMania 21 included former WCW Champion David Arquette, Motörhead, Adam Sandler, Rob Schneider, Billy Gibbons from ZZ Top, The Black Eyed Peas, Billy Corgan from Smashing Pumpkins, Anthony Kiedis from Red Hot Chili Peppers, Ice Cube, Carmen Electra, Sylvester Stallone, Marg Helgenberger from CSI: Crime Scene Investigation, and former MADtv cast member Will Sasso.
• This WrestleMania, along with the preceding one and the following one, would all take place from the three locations that hosted WrestleMania 2, New York, Chicago, and Los Angeles (This one from Los Angeles, WrestleMania XX from New York, and WrestleMania 22 from Chicago).