In professional wrestling, championships may be unified to consolidate the number of championships in a given promotion, or to add legitimacy and prestige to a certain title's lineage. In a title-for-title match, one of three things will happen:
- One of the championships is dropped
- A brand new championship is created
- Both championships remain active and are defended and lost together under one name, but title changes reflect each individual title's history
- The first two prominent unifications of titles in the United States were done by Nikita Koloff. In 1986, he unified the NWA National Heavyweight Championship into his NWA United States Heavyweight Championship by defeating Wahoo McDaniel, and in 1987 he unified the (Mid-South) UWF Television Championship into his NWA World Television Championship by defeating Terry Taylor. In both cases, the unification process was started by Nikita's home promotion, Jim Crockett Promotions, upon absorbing another promotion (Georgia Championship Wrestling and the Mid-South UWF, respectively), and in both cases the titles from the absorbed promotions were abandoned.
- The Triple Crown Heavyweight Championship was created with the unification of the NWA International Heavyweight Championship, the PWF World Heavyweight Championship and the NWA United National Championship, when the NWA International Heavyweight Champion Jumbo Tsuruta defeated the PWF World Heavyweight and NWA United National Champion Stan Hansen on April 18, 1989.
- The Omaha World Heavyweight Championship (a championship belt created by promoters in Omaha, Nebraska) unified with the AWA World Heavyweight Championship when the titles was unified on September 7, 1963 when AWA World Heavyweight Champion Verne Gagne defeated Omaha World Heavyweight Champion Fritz Von Erich in Omaha, Nebraska. The Omaha version was abandoned after absorbed with the AWA World Heavyweight Championship.
- The AWA World Heavyweight Championship and the WCWA World Heavyweight Championship were unified to create the USWA Unified World Heavyweight Championship at SuperClash III, when the AWA World Heavyweight Champion Jerry "The King" Lawler defeated the WCCW World Heavyweight Champion Kerry Von Erich. The WCCW World Heavyweight Championship was quickly abandoned, and later the American Wrestling Association stripped the AWA World Heavyweight Championship from Jerry Lawler.
- The J-Crown, a combination of eight lightweight championships from various wrestling promotions, was defended mostly in Japan and Mexico. The title has since been abandoned and all championship belts returned to their home promotions.
- The WCW International World Heavyweight Championship was unified with the WCW World Heavyweight Championship when WCW World Heavyweight Champion Ric Flair defeated WCW International World Heavyweight Champion Sting at Clash of the Champions XXVII. The WCW International World Heavyweight Championship was immediately abandoned, though the physical championship belt was used as the WCW World Heavyweight Championship as it originally had in 1991.
- The ECW FTW Heavyweight Championship (an unrecognized title created by Tazz) was unified with the ECW World Heavyweight Championship on March 21, 1999 at Living Dangerously when ECW World Heavyweight Champion Taz defeated ECW FTW Heavyweight Champion Sabu. The FTW title was abandoned when Taz continued to defend the ECW World title.
- The WCW United States Championship was unified with the WWF Intercontinental Championship on November 18, 2001 at Survivor Series when United States Champion Edge defeated Intercontiental Champion Test. The United States title was abandoned, then revived as the WWE's United States Championship in 2003 by Stephanie McMahon as a SmackDown!-exclusive title.
- The WCW Tag Team Championship was unified with the WWF Tag Team Championship at Survivor Series in 2001, when the WCW Tag Team Champions, The Dudley Boyz, defeated the WWF Tag Team Champions, The Hardy Boyz. The Dudleys won the WWF Tag Team Championship, and their WCW Tag Team Championship was absorbed into the WWF titles and abandoned. The titles had previously been held concurrently at SummerSlam (2001) when WCW Tag Team Champions The Brothers of Destruction defeated WWF Tag Team Champions Diamond Dallas Page and Chris Kanyon, although at that time both championship belts were held together instead of becoming one championship.
- The WCW Championship (rebranded as World Championship) and the WWF Championship were unified to create the Undisputed WWF Championship on December 9, 2001 at Vengeance when Chris Jericho defeated WWF Champion Stone Cold Steve Austin and World Champion The Rock in the same night. Essentially, the WWF Championship became the Undisputed Championship while the former WCW Championship was retired, although the championship belts used to represent the two championships would adorn the Undisputed WWF Champion for several months afterwards, up until a single championship belt was introduced to Triple H in April 2002.
- The WWE European Championship was unified with the WWE Intercontinental Championship in July 2002, when Intercontinental Champion Rob Van Dam defeated European Champion Jeff Hardy on Raw in a title unification match. The European title was abandoned as a separate championship.
- The WWE Hardcore Championship was unified with the WWE Intercontinental Championship in August 2002, when Intercontinental Champion Rob Van Dam pinned Hardcore Champion Tommy Dreamer. The Hardcore Championship was abandoned soon after.
- The WWE Intercontinental Championship was unified with the World Heavyweight Championship at No Mercy when World Heavyweight Champion Triple H defeated Intercontinental Champion Kane. The Intercontinental Championship was immediately abandoned, then revived in May 2003 by Raw Co-General Manager Stone Cold Steve Austin.
- The WWA World Heavyweight Championship was unified with the NWA World Heavyweight Championship when NWA World Heavyweight Champion Jeff Jarrett defeated WWA World Heavyweight Champion Sting on May 25, 2003 in Auckland, New Zealand in an inter-promotional match.
- The ROH Pure Championship was unified with the ROH World Championship when ROH World Champion Bryan Danielson defeated ROH Pure Champion Nigel McGuinness in Liverpool, England on August 12, 2006, in a match contested under pure wrestling rules with the stipulation that both championships could be lost by disqualification or countout.
- The International Wrestling Association unified the IWA World Heavyweight Championship with the WWC Universal Heavyweight Championship when the World Wrestling Council's champion abandoned the company and participated in a unification match which was recognized by the National Wrestling Alliance, in the process creating the first Undisputed World Heavyweight Champion in Puerto Rico.
- The Inoki Genome Federation version of the IWGP Heavyweight Championship unified with the New Japan Pro Wrestling's version of the IWGP Heavyweight Championship when NJPW's IWGP Heavyweight Champion Shinsuke Nakamura defeated IGF's IWGP Heavyweight Champion Kurt Angle in Tokyo on February 17, 2008. The titles are unified due to a working agreement between Total Nonstop Action Wrestling and New Japan Pro Wrestling in which Angle wrestles for TNA.
- The World Tag Team Championship was unified with the WWE Tag Team Championship, in a dark match before WrestleMania XXV, when WWE Tag Team Champions The Colóns (Carlito and Primo) defeated World Tag Team Champions John Morrison and The Miz in Houston, Texas on April 5, 2009 to become the "Unified WWE Tag Team Champions". Both titles, however, would remain independently active until the World Tag Team Championship was formally decommissioned in August 2010. The WWE Tag Team Championship continued and dropped the "unified" moniker.
- The original WWE Women's Championship was unified with the WWE Divas Championship at the Night of Champions pay-per-view in September 2010. Divas Champion Melina faced self-professed co-WWE Women's Champion Michelle McCool in a lumberjill match. McCool won the match due to interference from Layla to unify the two titles. Following the win, the Women's Championship was retired after 54 years and the Divas Championship became briefly known as the "Unified WWE Divas Championship".
- The World Heavyweight Championship was unified with the WWE Championship to create the WWE World Heavyweight Championship at TLC: Tables, Ladders & Chairs in December 2013. WWE Champion Randy Orton defeated World Heavyweight Champion John Cena in a Tables, Ladders, and Chairs match to unify both championships and become the new WWE World Heavyweight Champion. The new championship retained the lineage of the WWE Championship and the World Heavyweight Championship was retired, although the championship belts used to represent the two championships would adorn the WWE World Heavyweight Champion for several months afterwards, up until a single championship belt was introduced to Brock Lesnar in August 2014 on the Raw after Summerslam.
- The GFW Global Championship was unified with the Impact Wrestling World Heavyweight Championship (former TNA World Heavyweight Championship) to create the Unified GFW World Heavyweight Championship at Slammiversary XV in July 2017. GFW Global Champion Alberto El Patron defeated Impact Wrestling World Heavyweight Champion Lashley to unify both championships and become the Unified World Heavyweight Champion. The new championship retained the lineage of the TNA/Impact Wrestling World Heavyweight Championship and the GFW Global Championship was retired, although the championship belts used to represent the two championships would adorn the Unified GFW World Heavyweight Champion.
- The GFW Women's Championship was unified with the Impact Wrestling Knockouts Championship (former TNA Knockouts Championship) to create the Unified GFW Knockouts Championship at Slammiversary XV in July 2017. GFW Women's Champion Sienna defeated Impact Wrestling Knockouts Champion Rosemary to unify both championships. The new championship retained the lineage of the TNA/Impact Wrestling Knockouts Championship and the GFW Women's Championship was retired.
- "NWA National Heavyweight Title". Wrestling-Titles.com. Retrieved 7 February 2019.
- "411MANIA". Going Old School: Starrcade ’87. Retrieved 7 February 2019.
- Emelett, Ed (September 1995). "Japan's Triple Crown: "It's the Most Important Title in the World!"". Pro Wrestling Illustrated. London Publishing Co.: 28. ISSN 1043-7576.
- "World Heavyweight Title (Omaha)". Wrestling-Titles.com. Retrieved 7 February 2019.
- Royal Duncan and Gary Will (2000). "American Wrestling Association World Heavyweight Title". Wrestling Title Histories. Archeus Communications. ISBN 0-9698161-5-4.
- "J-CROWN Octuple Title Unification Tournament". Wrestling-Titles.com. Retrieved 7 February 2019.
- "411MANIA". The Chrononaut Chronicles: Clash of the Champions XXVII. Retrieved 7 February 2019.
- "ECW Living Dangerously 1999 « Events Database « CAGEMATCH - The Internet Wrestling Database". www.cagematch.net. Retrieved 7 February 2019.
- "The complex history of WWE's era of unification". WWE. Retrieved 7 February 2019.
- The World Wrestling Entertainment Yearbook 2003 Edition. Simon and Schuster. 30 June 2008. ISBN 9780743480628. Retrieved 7 February 2019 – via Google Books.
- "WWE RAW #483 « Events Database « CAGEMATCH - The Internet Wrestling Database". www.cagematch.net. Retrieved 7 February 2019.
- "WWE No Mercy". www.prowrestlinghistory.com. Retrieved 7 February 2019.
- "WWA World Heavyweight Title (Australia)". Wrestling-Titles.com. Retrieved 7 February 2019.
- "Title History". web.archive.org. 10 June 2008. Archived from the original on 2008-06-10. Retrieved 7 February 2019.
- "IWA - Historica Unificacion en la IWA". web.archive.org. 17 February 2008. Archived from the original on 2008-02-17. Retrieved 7 February 2019.
- "WWE News, RAW Results, Smackdown Results". Retrieved 7 February 2019.
- "WWE: Inside WWE > Title History > World Tag Team > 20090405 - Carlito & Primo". web.archive.org. 8 April 2009. Archived from the original on 2009-04-08. Retrieved 7 February 2019.
- "Divas Championship". WWE. Retrieved 7 February 2019.
- "CALDWELL'S WWE TLC PPV RESULTS 12/15: Live, in-person coverage of Cena vs. Orton unification match from Houston". www.pwtorch.com. Retrieved 2019-02-07.
- "7/2 Powell's GFW/Impact Wrestling Slammiversary live review: Lashley vs. Alberto El Patron to unify the GFW and Impact Wrestling Championships, Scott Steiner and Josh Mathews vs. Jeremy Borash and Joseph Park, Sonjay Dutt vs. Low Ki in a best of three falls match for the X Division Championship". prowrestling.net. Retrieved 2019-02-07.