Don Katsuaki Nomura (団 野村, Dan Nomura; born Donald Engel, May 17, 1957) is a Japanese sports agent who primarily represents baseball players. He is best known for convincing Nippon Professional Baseball players Hideo Nomo and Alfonso Soriano to retire from the league to sign with Major League Baseball in the 1990s, as well as negotiating for Hideki Irabu to be sent to the New York Yankees like he requested instead of the San Diego Padres, which led to the NPB dissolving the reserve clause and paved the way for Japanese Baseball players playing in the MLB.

Nomura was born Donald Engel at St. Luke's International Hospital in Chūō, Tokyo, to a Japanese mother, Yoshie Itō and a Jewish American father, Alvin George Engel. His mother left the family when Don was six, leaving his father to care for him and his younger brother Kenneth. He attended St. Mary's International School, a private, English-speaking Catholic school in Tokyo, until he was kicked out for fighting at the age of 16. Nomura then attended Chofu High School, then transferred to Zama High School, where he played baseball and graduated in 1975. During this time, he began visiting his mother, who had changed her name to Sachiyo [ja] and married NPB catcher and manager Katsuya Nomura. After completing high school, Nomura enrolled at California State Polytechnic University in Pomona, California where he studied and played baseball from 1975–77.

In 1977, at the age of 21, the Japanese Home Ministry would no longer allow Nomura to hold a US-Japan dual citizenship, requiring him to choose one. He chose Japanese citizenship. Nomura's decision was influenced by a NPB restriction that allowed only two foreign players per team at the time. He then assumed the name Katsuaki Itō (Itou Katsuaki) until his stepfather adopted him that same year, at which time he took the name Don Katsuki Nomura. Commenting on his new Japanese name, Nomura remarked, "It helped me get into places and meet people". He began playing on a minor league team affiliated with the Yakult Swallows the next year as a utility infielder.

In 1981, he was released after playing four seasons with the team because of poor performance. The same year, Nomura's 62-year-old father, Alvin Engel, committed suicide in Hawaii via carbon monoxide poisoning. Nomura traveled to Hawaii to pick up his father's ashes and return them to Japan.

In December of the same year, Nomura moved to Los Angeles with his new wife. There he worked a series of odd jobs including a non-paying scout for the Milwaukee Brewers, travel agent, janitor, waiter, driver, liquor store clerk, tour coordinator, translator and so on. For a time, Nomura was forced to send his wife and infant daughter back to Japan while he lived in his car in Los Angeles because of his poor financial state. By 1985, he had saved enough money to rent an apartment and bring his family back to L.A. Nomura then converted $1,000 to $41,000 while playing baccarat in Las Vegas. The money helped him to buy an apartment building in L.A. for $250,000 that he later sold for $400,000.

In 1989, Nomura borrowed money to buy 50% of the Salinas Spurs, an unaffiliated Class-A baseball team in the California League. NPB teams sent their high school draftees to Nomura's Spurs for training. As a teenager, baseball player Mac Suzuki worked in the team's clubhouse until he began playing with the Spurs in 1992. That year, Suzuki became Nomura's first client when he signed him to a personal representation contract. Nomura then negotiated with the Seattle Mariners and later earned Suzuki a million-dollar signing bonus. In 1992, Nomura sold the Spurs to a group in San Bernardino. He founded the Los Angeles-based company KDN Sports, Inc. and became a full-time sports agent.

In 1994 Nomura discovered a loophole in the NPB player contract and working agreement between MLB and NPB. According to the 1967 working agreement between MLB and NPB, NPB players could not sign a contract with an MLB team until they reached free agency after 10 years of service or unless their team sold their contract to an MLB team. However, a player who "voluntarily retired" from NPB was no longer bound to their NPB team outside Japan and was free to sign overseas without violating the working agreement.

After the 1994 season Nomura assisted star NPB pitcher Hideo Nomo in testing the loophole. After failing to reach a contract agreement with the Kintetsu Buffaloes, Nomo retired from NPB and signed with the Los Angeles Dodgers in 1995.