There have been thousands of professional boxers over the years but most of them, even the greats, lost a bout or two along the way. Retiring undefeated in the sport is quite an accomplishment. This list features the only 13 boxers in history who were world champions and managed to finish their careers without losing a fight.

Floyd Mayweather Jr. (49-0) was also an undefeated titleholder, but he’ll be taking on Conor McGregor of the UFC on August 26th. The list may grow in the future as there are currently several world champions who are yet to taste defeat. These include Anthony Joshua, Terence Crawford, Joseph Parker, Deontay Wilder, Andre Ward, Gilberto Ramirez, Keith Thurman, Errol Spence Jr., and Gennady Golovkin.

13. Terry Marsh

England’s Terry Marsh made this list in his second-last career pro fight when he stopped Joe Manley for the IBF Jr. Welterweight Title in April of 2007. Marsh then defended it four months later with a seventh-round knockout of Akio Kameda and duly hung up his gloves with a near-perfect record of 26-0-1 with 10 Kos. The only blemish on his record was an eight-round draw with Lloyd Christie in 1982. Although Marsh had a fine amateur career, was a European Champion, and went undefeated as a pro, he didn’t really take on any elite opponents during his short career from 1981 to 1987. The former royal marine suffers from epilepsy and recently took up the hybrid sport of chess-boxing, becoming a welterweight champion. He’s also dabbled in acting and politics.

12. Harry Simon

Fighting from 1994 to 2016, Harry Simon of Namibia was a WBO Junior Middleweight Champion. He won the crown via a decision over Winky Wright in 1998 and went on to defend it four times. He vacated the title and won it back in April, 2002 by beating Armand Krajnc. However, Simon was involved in a couple of car accidents and was stripped of the belt when he was too injured to defend it. The ex-champ was sentenced to two years in prison in 2005 for culpable homicide in one of the accidents, but appealed it and returned to the ring in 2007 after a five-year absence. Simon served his sentence from 2007 to 2009 and once again returned to the ring in 2010 as a light heavyweight. He retired with a perfect mark of 30-0 with 22 Kos and a knockout ratio of 73 per cent. Other than Wright and Krajnc, Simon fought mostly Grade B opposition, with foes such as Wayne Alexander, Hacine Cherifi and Rodney Jones.

11. Pichit Sitbangprachan

Thailand’s Pichit Sitbangprachan also used the name Supap Hanwichachai and went 24-0 as a flyweight with 18 Kos and all of his contests coming in his homeland. After turning pro in 1988, the southpaw won the IBF Championship in November, 1992 and held it until mid-1994. He defended the belt five times and also fought several non-title bouts while holding the crown. He retired for the first time in 1994 and gave up the belt, but returned in 1996 for one bout before retiring again. However, he back four years later for two more fights before hanging the gloves up for good. Sitbangprachan’s best wins were over Miguel Martinez, Rodolfo Blanco, Dan Nietes, Antonio Perez and Jose Luis Zepeda.

10. Ji-won Kim

Ji-won Kim hails from South Korea and was a boxing star in the amateurs with several gold medals to his name in various tournaments across the globe. The southpaw turned pro in 1982, won a few regional titles and then stopped fellow countryman Suh Sung-in for the IBF Super Bantamweight Title in January, 1985. Kim defended the championship four times, three by KO and three times against ex-world champs, before retiring as the undefeated belt holder at the end of 1986. His biggest wins were against Bobby Berna, Suh Sung-in, Rudy Casicas and Ruben Palacios. The reason Kim walked away from pro boxing after just four years was to sing and act in the theatre. He didn’t win all his bouts though as Kim fought to a pair of 10-round draws with Neptali Alamaq early in his career and went 16-0-2 with seven Kos.

9. Mihai Leu

Mihai Leu was born in Romania, but fought his entire pro career out of Germany and that’s why he also went by the name Michael Loewe. Leu was a four-time national champion as an amateur with a record of 190-10 and then fought professionally from 1991 to 1997 with a mark of 28-0 with 10 Kos. He won the vacant WBO Welterweight Championship in 1997 by decision over Santiago Samaniego. Leu defended the belt seven months later by majority decision over Michael Carruth and that was the end of his pro boxing days. Unfortunately, he didn’t take on any elite opponents during his career. He had suffered an injury which wouldn’t allow him to box anymore, but then followed in his father’s and brother’s footsteps by turning to rally driving. He became quite good at it and later won a Romanian national championship.

8. Jimmy Barry

We’re going to travel back in time now to another era of boxing to visit Jimmy ‘The Little Tiger’ Barry of Chicago. Barry fought from 1891 to 1899 with an official record of 59-0-10 with 40 kos. Barry boxed to 10 draws in his career, including each one of his last nine fights. He won the vacant World Bantamweight Title in December, 1894 and retired as the undefeated king in September of 1899. Walter Croot, one of Barry’s opponents, died the day after their bout in December, 1897 and the champion was charged with manslaughter. However, the charges were dropped after examinations revealed Croot’s death was caused when his head bounced off the floor after being knocked down. The tragedy then resulted in the introduction of the padded ring canvas. Barry felt terrible about Croot and fought 10 times after the accident with just one win.

7. Dmitry Pirog

Dmitry Pirog of Russia had a relatively short pro career from 2005 to 2012. He retired due to a back problem, but managed to go 20-0 with 15 Kos. He also got his hands on the WBO Middleweight Championship in 2010 and held onto it for two years. Pirog reportedly went 200-30 as an amateur and won several regional pro belts before meeting Daniel Jacobs for the vacant WBO Middleweight Championship in July, 2010. Jacobs was the clear favourite, but Pirog pulled of a huge shock by stopping the unbeaten American in the fifth round. He defended the title three times and was then stripped of it for opting to meet fellow champion Gennady Golovkin rather than defend it against Hassan N’Dam N’Jikam, who was the WBO’s interim champ. Unfortunately, Pirog retired before meeting Golovkin, but his biggest wins came over Jacobs, Nobuhiro Ishida, Gennady Martirosyan and Kofi Jantuah.

6. Jack McAuliffe

Like Jimmy Barry, Jack McAuliffe of Cork, Ireland boxed in the late 19th century. He was a lightweight who fought in America from 1885 to 1897 with an official ring record of and 28-0-10 with 20 kos. He also fought many more unofficial bouts and was known as ‘The Napoleon of the Ring.’ Barry was recognized as the very first Lightweight Champion of the World between 1886 and 1893. The hall of famer started out in the amateur ranks two years before turning pro. Boxing was a lot different in that era as McAuliffe often fought more than 20 rounds with his longest bout being recorded at 64 rounds. McAuliffe was the first world champion to go undefeated when he decided he’d had enough in 1897.

5. Edwin Valero

Edwin Valero of Venezuela, lived a short, tragic life, but accomplished a lot in the ring before it ended at the age of 28 in 2010. He turned professional in 2002 after an excellent amateur career at 86-5 with 57 Kos and managed to go 27-0 as a pro with every fight ending in a knockout. The southpaw was also the first boxer in history to start his pro career at 18-0 with 18 first-round knockouts. Valero won the WBA Super Featherweight Title in 2006 by stopping Vicente Mosqueran and defended it four times. He then moved up to lightweight and won the vacant WBC Belt against Antonio Pitalua. Valero defended it against Hector Velasquez and Antonio DeMarco before things fell apart. He was arrested in March, 2010 for allegedly assaulting his wife, but Valero said she had fallen down the stairs. The boxer was sent for psychiatric treatment and just a month later was hauled in for murdering his wife. Valero reportedly admitted the killing and hung himself in his cell early the next day.

4. Sven Ottke

Another excellent amateur boxer who turned pro and went unbeaten was three-time Olympian Sven Ottke of Germany. He went 256-47-5 as an amateur and then compiled a record of 34-0 with six Kos as a pro from 1997 to 2004. He didn’t have much in the way of power, but Ottke’s boxing skills enabled him to win the WBA (Super) and IBF Super Middleweight Titles and reign as a world champion for six years while retiring with both belts. Ottke defended his championships a total of 21 times with wins over the likes of Armand Krajnc, Robin Reid, Byron Mitchell, Joe Gatti, Thomas Tate, Charles Brewer, Anthony Mundine and Glen Johnson. He also beat some top opponents as an amateur including future world champions Michael Moorer, Chris Byrd and Antonio Tarver.

3. Joe Calzaghe

Southpaw Joe Calzaghe was born in London, England, but moved to Wales when he was a toddler. He started boxing as a nine-year-old and went 112-10 as an amateur. He turned pro in 1993 and didn’t hang up his gloves until 2008. Along the way Calzaghe racked up a perfect record of 46-0 with 32 Kos. ‘The Pride of Wales’ won the vacant WBO Super Middleweight Title with a win over Chris Eubank in October, 1997 and would later add the IBF, WBC and WBA (super) versions of the belt. He’s the longest-reigning champion in the history of the 168 lb. division and defended his title 21 times before moving up to light heavyweight for his last two bouts. Calzaghe then beat Bernard Hopkins for the Ring Magazine title and defended it against Roy Jones Jr. before retiring. As a super middleweight, the hall of famer beat some fine boxers such as Robin Reid, Omar Sheika, Mario Veit, Charles Brewer, Byron Mitchell, Jeff Lacy and Mikkel Kessler.

2. Ricardo Lopez

Mexico’s Ricardo “El Finito” Lopez was one of the great little men in boxing and also arguably has the best record of the 13 undefeated champions. He fought from 1985 to 2001 with a near-perfect mark of 51-0-1 with 38 Kos. He won the WBC and Lineal Minimumweight Titles in 1990 when he stopped Japan Hideyuki Ohashi of Japan in the fifth round in Tokyo. Lopez then went on to defend his belt 21 times to set a new record for the division. The hall of famer added the WBO Minimumweight Crown in 1997 with a knockout over Alex Sanchez and beat Rosendo Alvarez the next year to win the WBA version of the title. In his very next fight he moved up to light flyweight and captured the IBF Crown in that division. Lopez defended it twice and then retired as one of boxing’s all-time great champions. In addition, he went unbeaten in the amateurs and became the first man to never lose a bout in his career while his 26 title bouts without defeat are a record shared with Floyd Mayweather Jr. and Joe Louis.

1. Rocky Marciano

The most famous boxer on this list is undoubtedly former heavyweight champion and hall of famer Rocky Marciano of Massachusetts. ‘The Brockton Blockbuster’ ranks as one of the greatest ever with his record of 49-0 with 43 Kos between 1947 and 1955. Marciano possessed tremendous power even though he was just over 5-feet-10-inches tall. He fought just 12 amateur bouts while in the army and then won the World Heavyweight Title in his 43rd pro fight by stopping Jersey Joe Walcott in the 13th round. Marciano defended his championship six times, including a rematch with Walcott, before retiring at the age of 32. He contemplated a comeback in 1959, but ultimately decided against it. Marciano would lose his life in a small plane crash in 1969 when he was 45, just a day before his birthday. His boxing record also includes wins over Archie Moore, Don Cockell, Ezzard Charles (twice), Lee Savold, Harry Matthews and the great Joe Louis.