Tom Okker (born February 22 1944), nicknamed The Flying Dutchman and Tom the Twitch, is a former Dutch tennis player. He was ranked among the world's top 10 singles players for seven consecutive years, 1968 through 1974, reaching a career high of World No. 3 in 1969. He also was ranked World No. 1 in doubles in 1969.
Okker was the Dutch champion from 1964 through 1968. In 1968, he turned professional and won his first important tournament in singles and doubles (with Marty Riessen) at the Italian Open. At Wimbledon, Okker reached the quarterfinals in 1968 and the semifinals in 1978. He achieved his best result in a Grand Slam tournament in 1968, when he lost the final of the U.S. Open to Arthur Ashe 14-12, 5–7, 6–3, 3–6, 6–3.
Okker won 31 singles titles. As of 2000, 20 years after his retirement, Okker’s 31 career "open tennis" singles victories (combined ATP tour, Grand Prix, and WCT tournaments) still ranked 20th all-time. Among Okker’s singles titles were the 1970 German Open and Belgian Open, 1973 Dewar Cup and Canadian Open, and 1974 WCT Rothmans. He also was the runner-up in 24 singles tournaments.
Despite his success in singles, Okker is mostly remembered for being one of the most successful men's doubles player of all time. Okker won two Grand Slam doubles titles, the U.S. Open in 1976 (with Riessen) and the French Open (with John Newcombe) in 1973. In total, Okker won 78 doubles events, a record that was finally broken by Todd Woodbridge in 2005. Okker’s other doubles titles include: 1973 Italian Open; 1973 London Grass Courts (with Riessen); 1973 Spanish Open (with Ilie Nastase); 1975 Opel International (with Arthur Ashe); and 1978 WCT World Doubles (with Wojtek Fibak).
One of the first tennis professionals to win at least U.S. $1 million in career prize money, Okker's WTC career earnings stood at U.S. $1,257,200 when he retired in 1980.
Between 1964 and 1981, Okker represented The Netherlands in Davis Cup play, where he was 15-20.
In 1965 Okker won both the singles and the mixed doubles titles at the Maccabiah Games in Israel.
Okker was a fan favorite with his animated, quick-footed play. He was a slight but canny player who often defeated larger, more powerful opponents.
| Year | Championship | Opponent in Final | Score in Final |
| 1968 | U.S. Open | Arthur Ashe | 14–12, 5–7, 6–3, 3–6, 6–3 |
| No. | Date | Tournament | Surface | Opponent in the final | Score |
| 1. | 1969 | Rome, Italy | Clay | Bob Hewitt | 10–8, 6–8, 6–1, 1–6, 6–0 |
| 2. | 1969 | Monte Carlo, Monaco | Clay | John Newcombe | 8–10, 6–1, 7–5, 6–3 |
| 3. | 1969 | Hilversum, Netherlands | Hard | Tom Gorman | 6–3, 4–6, 7–6 |
| 4. | 1969 | Paris Indoor, France | Carpet | Earl Butch Buchholz | 8–6, 6–2, 6–1 |
| 5. | 1970 | Hilversum, Netherlands | Hard | Roger Taylor | 4–6, 6–0, 6–1, 6–3 |
| 6. | 1970 | Hamburg, Germany | Clay | Ilie Năstase | 4–6, 6–3, 6–3, 6–4 |
| 7. | 1971 | Louisville WCT, U.S. | Clay | Cliff Drysdale | 3–6, 6–4, 6–1 |
| 8. | 1971 | Quebec WCT, Canada | Indoor | Rod Laver | 6–3, 7–6, 6–7, 6–4 |
| 9. | 1972 | Chicago WCT, U.S. | Carpet | Arthur Ashe | 4–6, 6–2, 6–3 |
| 10. | 1973 | Washington WCT, U.S. | Carpet | Arthur Ashe | 6–3, 6–7, 7–6 |
| 11. | 1973 | Hilversum, Netherlands | Clay | Andrés Gimeno | 2–6, 6–4, 6–4, 6–7, 6–3 |
| 12. | 1973 | Montreal, Canada | Hard | Manuel Orantes | 6–3, 6–2, 6–1 |
| 13. | 1973 | Seattle, U.S. | Other | John Alexander | 7–5, 6–4 |
| 14. | 1973 | Chicago, U.S. | Carpet | John Newcombe | 3–6, 7–6, 6–3 |
| 15. | 1973 | Madrid, Spain | Clay | Jaime Fillol | 4–6, 6–3, 6–3, 7–5 |
| 16. | 1973 | London, United Kingdom | Carpet | Ilie Năstase | 6–3, 6–4 |
| 17. | 1974 | Toronto WCT, Canada | Carpet | Ilie Năstase | 6–3, 6–4 |
| 18. | 1974 | Rotterdam, Netherlands | Carpet | Tom Gorman | 4–6, 7–6, 6–1 |
| 19. | 1975 | Nottingham, United Kingdom | Grass | Tony Roche | 6–1, 3–6, 6–3 |
| 20. | 1975 | Paris Indoor, France | Hard (i) | Arthur Ashe | 6–3, 2–6, 6–3, 3–6, 6–4 |
| 21. | 1977 | Richmond WCT, U.S. | Carpet | Vitas Gerulaitis | 3–6, 6–3, 6–4 |
| 22. | 1979 | Tel-Aviv, Israel | Hard | Per Hjertquist | 6–4, 6–3 |
| No. | Date | Tournament | Surface | Opponent in the final | Score |
| 1. | 1968 | Gstaad, Switzerland | Clay | Cliff Drysdale | 6–3, 6–3, 6–0 |
| 2. | 1968 | U.S. Open, New York City | Grass | Arthur Ashe | 14–12, 5–7, 6–3, 3–6, 6–3 |
| 3. | 1969 | Gstaad, Switzerland | Clay | Roy Emerson | 6–1, 12–14, 6–4, 6–4 |
| 4. | 1969 | Hamburg, Germany | Clay | Tony Roche | 6–1, 5–7, 7–5, 8–6 |
| 5. | 1970 | Gstaad, Switzerland | Clay | Tony Roche | 7–5, 7–5, 6–3 |
| 6. | 1971 | Monte Carlo, Monaco | Clay | Ilie Năstase | 3–6, 8–6, 6–1, 6–1 |
| 7. | 1971 | Gstaad, Switzerland | Clay | John Newcombe | 6–2, 5–7, 1–6, 7–5, 6–3 |
| 8. | 1971 | Montreal, Canada | Clay | John Newcombe | 7–6, 3–6, 6–2, 7–6 |
| 9. | 1971 | Toronto WCT, Canada | Carpet | John Newcombe | 7–6, 3–6, 6–2, 7–6 |
| 10. | 1971 | Vancouver WCT, Canada | Outdoor | Ken Rosewall | 6–2, 6–2, 6–4 |
| 11. | 1972 | Boston WCT, U.S. | Hard | Robert Lutz | 6–4, 2–6, 6–4, 6–4 |
| 12. | 1972 | Stockholm, Sweden | Hard (i) | Stan Smith | 6–4, 6–3 |
| 13. | 1972 | Rotterdam WCT, Netherlands | Carpet | Arthur Ashe | 3–6, 6–2, 6–1 |
| 14. | 1973 | Washington D.C., U.S. | Clay | Arthur Ashe | 6–4, 6–2 |
| 15. | 1973 | Los Angeles, U.S. | Hard | Jimmy Connors | 7–5, 7–6 |
| 16. | 1973 | Masters, Boston | Carpet | Ilie Năstase | 6–3, 7–5, 4–6, 6–3 |
| 17. | 1974 | Washington WCT, U.S. | Carpet | Ilie Năstase | 6–3, 6–3 |
| 18. | 1974 | Boston, U.S. | Clay | Björn Borg | 7–6, 6–1, 6–1 |
| 19. | 1974 | Stockholm, Sweden | Hard (i) | Arthur Ashe | 6–2, 6–2 |
| 20. | 1975 | Rotterdam WCT, Netherlands | Carpet | Arthur Ashe | 3–6, 6–2, 6–4 |
| 21. | 1975 | Johannesburg WCT, South Africa | Hard | Buster Mottram | 6–4, 6–2 |
| 22. | 1975 | Stockholm WCT, Sweden | Carpet | Arthur Ashe | 6–4, 6–2 |
| 23. | 1978 | Hilversum, Netherlands | Clay | Balázs Taróczy | 2–6, 6–1, 6–2, 6–4 |
Okker, who is Jewish, was inducted into the International Jewish Sports Hall of Fame in 2003.