Konstantin "Kostya the Goit" Tszyu (born September 19, 1969) is a Russian- born boxer of mixed Russian, Korean and Mongol descent. He has Australian and Russian citizenship and is a two time world junior welterweight champion, including a period of time as the undisputed junior welterweight champion. The son of a fitter in a metal factory and a nurse, Tszyu was born in a town named Serov, near the Ural Mountains.

Tszyu and his family, including his sister, used to share an apartment with another family, and Tszyu used to sleep on the floor. Tszyu was hyperactive as a child, and his father decided to take him to a boxing gym, where he would channel that energy by fighting older boys. Soon, Tszyu impressed Russia's amateur team coaches and he was sent to the Soviet Union's amateur boxing travelling training camps, where he got to visit more than 30 countries while training and fighting in tournaments. He trained with that group 250 days a year, and won various tournaments, such as amateur boxing's world championships. He also participated in the Olympic Games. At the Cuban world championship tournament in 1987, he came in second place, and at the Seoul Olympic games, he lost in the third round.

Kostya was a member of the Soviet military too, but since he was selected as an elite athlete, he did not have to participate in any wars. He fought at the world championships once again, in Moscow in 1989, where he came in third place. In 1991, he went again to the amateur world championships, this time held in Sydney. This was a trip that would change his life forever. Not only was the third time his charm, but he felt enchanted with the sights of Sydney and its people, and decided he wanted to live in Australia. After the collapse of the Soviet Union, in 1992, Tszyu escaped from the Russian army and fled to Australia with his girlfriend, where they married in 1993 and became Australian citizens. Before marrying her, though, Tszyu had already turned professional, beating Darrell Hiles by a knockout in one round on March 1, 1992 at Melbourne.

Professional career Tszyu started raising his quality of opposition almost immediately. In his fourth professional bout, he met the former WBC Featherweight champion of the world Juan Laporte. In his sixth bout, he beat contender Sammy Fuentes by a knockout in the first. Fuentes would go onto win a world title years after being handily beaten by Tszyu in 1993, Steve Larrimore, Larry La Crousiere and Robert Rivera, went to Australia to fight Tszyu, and none lasted more than two rounds. The only man to last more than two rounds with Tszyu in '93 was Livingstone Bramble, a former world Lightweight champion, who lost by decision to Tszyu at Newcastle, Australia. In 1994, Hector Lopez,, Angel Hernandez, who had just come off of a loss after challenging Julio César Chávez for the WBC belt and Pedro Chinito Sanchez, from the Dominican Republic tried to beat Tszyu, but Tszyu beat Lopez by a decision in ten, Hernandez by a knockout in seven, and Sanchez by a knockout in four. After the win against Sanchez, Tszyu was ranked number one in the Jr. Welterweights.

Winning His First Title In 1995, he received his first world title shot when he fought IBF world junior welterweight champion Jake Rodriguez at Las Vegas, Nevada. Tszyu became world champion by knocking Rodriguez out in the sixth round, and then defended the world title, beating former world junior lightweight and junior welterweight champion Roger Mayweather by a decision in 12, Hugo Pineda by a knockout in 11, Cory Johnson by a knockout in four and Jan Bergman by a knockout in six. After this string of defences, Tszyu became a highly touted world champion by many boxing magazines, and many articles about him appeared on Ring Magazine, KO Magazine, and other American boxing publications.

Title Defences 1997 began for Tszyu when his defence against Leonardo Moro Mas was declared a no contest. For his next bout, however, Tszyu wasn't as lucky, and he lost for the first time, losing by a knockout in ten rounds to Vince Phillips, who also took with that, Tzsyu's world championship. He regrouped after that defeat, and came back to beat Ismael Chaves just before year's end. He retained the title once in 1999, knocking out former world champion Miguel Angel Gonzalez in ten, and twice in 2000, beating Arizona's fringe contender Ahmed Santos in eight, and a 38 year old Mexican legend Julio César Chávez, the former world champion, in six at Phoenix, Arizona.

Taking Time Off Tszyu had been slated for a possible 2006 rematch with Zab Judah and has even talked with the Mayweather camp about a possible future meeting, but has stated he will not consider any fights in 2006, and has seemingly not yet made a decision as to whether he will continue boxing at all. Tszyu competed on the Australian version of Dancing With the Stars, placing second. Tszyu's record currently stands at 31 professional wins (25 by knockout), two losses and one no contest. He is considered by many in Australia to be a national sports hero. Tszyu and his family reside in Sydney where his son attends St George Christian School.On the 30th of January 2007 rumours spread of a Tszyu comeback.