Pancho Segura, born Francisco Olegario Segura Cano (June 20, 1921), was a leading tennis player of the 1940s and 1950s, both as an amateur and as a professional. A crowd-pleaser with his winning smile, unathletic appearance, infectiously humorous manner, and unorthodox but deadly game, Segura was overshadowed during his long professional career by first Jack Kramer and then Pancho Gonzales; he won, however, many matches against the greatest players in the world and was particularly brilliant in the annual United States Professsional Championships. In spite of never winning any of the four Grand Slam titles as a young amateur, some sources later credit him with having a claim, as a professional, of being the World No. 1 tennis player for three consecutive years, 1950 through 1952.
In his 1979 autobiography Kramer included Segura in his list of the 21 greatest players of all time. He went on to say, "...and while his amateur record is of no consequence, he beat everyone in the pros but Gonzales and me. We beat him with good second serves." A year earlier, another World No. 1 player, Ellsworth Vines, the man that Kramer called the greatest player of all time at the height of his game, had published a lesser-known book called Tennis: Myth and Method, co-written with Gene Vier. Vines devotes the first part of the book to individual chapters about the ten greatest tennis players from Don Budge through the date of the book's publication. He considered Segura to be the fifth best of these ten great players, behind, in order, Budge, Kramer, Gonzales, and Rod Laver. Segura, however, ranked above Bobby Riggs, Ken Rosewall, Lew Hoad, Frank Sedgman, and Tony Trabert.
Vines also gives an expert's analysis of Segura's unusual playing style:
Two-handed forehand is most outstanding stroke in game's history; unbeatable unless opponent could avoid it. Improved as a professional by taking advantage of volleying ability he rarely used as an amateur. Backhand also better later in career. Returns serve brilliantly, particularly off right side where quicksilver moves give him unusual positioning talent. Serve only average for his class of player but well placed, as is overhead. Very deft volleyer, particularly off forehand. Lob and dropshot unsurpassed. Superb passing shots, change of pace, and asbolute consistency make him greatest "little man" to ever play the game.
Segura, Kramer writes in his autobiography, "was the one pro who brought people back. The fans would come out to see the new challenger face the old champion, but they would leave talking about the bandy-legged little sonuvabitch who gave them such pleasure playing the first match and the doubles. The next time the tour came to town the fans would come back to see Segoo." For this, according to Kramer, Segura made more than $50,000 in each of six or seven years during the 1950s, a time in which "there were very few baseball, football or basketball players making $50,000."
Born on a bus outside of Guayaquil, Ecuador, Segura moved to the United States in the late 1930s as a young man and is a citizen of both countries. Almost dying at his premature birth, Segura then suffered from both a pediatric double hernia that was eventually corrected by an operation when he was about 10 and from malaria. No more than 5'6" (1.68 m) tall, he grew up to have badly bowed legs from the rickets that he also had as a child because of an inadequate diet. In spite of this, he had extremely fast footwork and a devastating two-handed forehand that his frequent adversary and tennis promoter Jack Kramer once called "the greatest single shot ever produced in tennis". His father, a very large, powerful man, just barely managed to provide a meager living for his large family by working as the caretaker of Guayaquil's most exclusive tennis club; his small son, called morenito, "the little dark one" by his mother, was allowed to practice at the club by hitting balls off a wall with discarded rackets and to play on empty courts. Little Pancho also earned a few vital cents for his family by working as a ball boy for the members and, as he grew older and more proficient in tennis, as a hitting partner for them.
By the time he was 17 Segura had won a number of titles in Latin America and was offered a tennis scholarship at the University of Miami. He won the Intercollegiates for three straight years, in 1943, 1944, and 1945, and was also the number 3-ranked American player during those years. He won the U.S. Indoors in 1946 and U.S. Clay Courts in 1944 but was never able to win the national championship at Forest Hills, although he reached the semi-finals a number of times. Kramer writes that he lost "without distinction (to Tom Brown and Drobny) the two times he played Wimbledon, and really, nobody took Segoo seriously. He didn't speak English well, he had a freak shot, and on the grass scooting around in his long white pants with his bowlegs, he looked like a little butterball. A dirty butterball: his pants were always grass-strained."
Long before the Open era of tennis, Segura turned professional in 1947 and was an immediate hit with the spectators who came out to view the touring pros. According to Bobby Riggs, Jack Harris, the promoter of the forthcoming Riggs-Kramer tour of 1948, first attempted to sign Ted Schroeder to play the preliminary matches on the tour. Ultimately he failed and instead signed Segura to play the latest Australian amateur champion, Dinny Pails. Instead of a percentage of the gross receipts, as Riggs and Kramer were contracted for, Segura and Pails were each paid $300 a week. 
In the 1950-1951 professional tour Segura graduated to playing the headline match against Kramer, who had been the world’s best player for most of the last few years. He was beaten 58 matches to 27 but this was a noticeably better performance than Gonzales's record of 27 victories and 96 defeats against Kramer the year before. In the following tour, that of 1952-1953, Segura was once again reduced to playing the preliminary match, where he beat the Australian Ken McGregor 71 matches to 25.
For the calendar year of 1952, when Kramer, Don Budge, and Gonzales all played only sporadically, Segura was ranked as the World No. 1 player by the Professional Lawn Tennis Association, with Gonzales at No. 2.  He was at his best in the annual United States Pro Championship, where he won the title three years in a row from 1950 through 1952, beating Gonzales twice. He also lost in the finals four times over the years, losing to Gonzales three times and once to Butch Buchholz in 1962 when he was 41 years old.
Segura, says Kramer, probably played "more matches against top players than anyone in history. Besides my couple hundred, he must have played Gonzales a hundred and fifty, and Budge, Sedgman, Riggs, Hoad and Rosewall all around fifty apiece. I beat him about 80 percent of the time, and Gonzales also held an edge over him. He was close with Budge. Pails beat him 41-31 on the Kramer-Riggs tour, but that was when Segoo was still learning how to play fast surfaces. With everybody else, he had the edge: Sedgman, Rosewall, Hoad, Trabert, McGregor."
Discussing the greatest tennis strokes of all time, Kramer says that, "Possibly Budge's backhand was the better stroke, I'll have to accept that judgment. But put a gun to my head, and I'd have to say the Segura forehand because he could disguise it so much better and hit so many more angles." Kramer goes to say, however, that Segura's "trouble was that he never learned to exploit this great weapon because he used it too often. He didn't know how to pace himself and pick his spots. Perhaps he was too quick for his own good; he was so fast he could run around anything and get to his forehand.... he probably hit his forehand four times as much as his backhand.... Segoo went too far and wasted himself in the process." Curiously, Segura did not develop a complementary two-handed backhand, a very common stroke since the 1970s; according to Segura, it did not occur to him to try one until his touring career was over.
At a professional event in 1951 the forehand drives of a number of players were electronically measured. Pancho Gonzales hit the fastest, 112.88 mph, followed by Jack Kramer at 107.8 and Welby Van Horn at 104. Since it was generally assumed at the time that Segura had the hardest forehand among his contemporaries, it is possible that he was not present at that event. 
After retiring from the Tour in 1962 Segura became the head professional and teaching pro at the Beverly Hills Tennis Club, where, for a number of years his charismatic personality, easy manner with movie stars, and friendship with the world's leading tennis players were important in helping the club increase its membership. Using the club as a base, he helped instructed and help train a number of leading young players, including Stan Smith and Jimmy Connors. He was particularly instrumental in training Connors, who, along with his mother, moved from East St. Louis to Beverly Hills at age 16 to be intensively coached by Segura. In early 1971, Segura left Beverly Hills to accept a more lucrative deal at La Costa in Carlsbad, California, one of the first so-called "destination resorts". He remained prominent for the next few years as Connors coach but by 1975 the younger star's domineering mother, Gloria, grew jealous at Segura's prominence and her own lack of recognition in training her son, and she effectively removed Segura from Connors' life. It was not until 30 years later, in 2005, that Connors began to publicly acknowledge the debt he owed to Segura.
Before the famous "Battle of the Sexes" tennis match between Billie Jean King and Bobby Riggs in 1973, he openly supported Riggs. When King won the match, Segura declared disgustedly that Riggs was only the third best senior player, behind himself and Gardnar Mulloy, and challenged King to another match. King refused.
Segura was inducted into the International Tennis Hall of Fame in Newport, Rhode Island, in 1984.
- Writing in 1979, Kramer considered the best ever to have been either Don Budge (for consistent play) or Ellsworth Vines (at the height of his game). The next four best were, chronologically, Bill Tilden, Fred Perry, Bobby Riggs, and Pancho Gonzales. After these six came the "second echelon" of Rod Laver, Lew Hoad, Ken Rosewall, Gottfried von Cramm, Ted Schroeder, Jack Crawford, Pancho Segura, Frank Sedgman, Tony Trabert, John Newcombe, Arthur Ashe, Stan Smith, Björn Borg, and Jimmy Connors. He felt unable to rank Henri Cochet and René Lacoste accurately but felt they were among the very best.
- Tennis: Myth and Method, by Ellsworth Vines and Gene Vier, Viking Press, New York, pages 65–66
- Tennis Is My Racket, by Bobby Riggs, New York, 1949, page 16.
- The History of Professional Tennis (2003) Joe McCauley, page 57.
- The History of Professional Tennis, Joe McCauley, page 57
- The Game, My 40 Years in Tennis (1979), Jack Kramer with Frank Deford (ISBN 0-399-12336-9)
- The History of Professional Tennis (2003), Joe McCauley
- Tennis Is My Racket (1949), Bobby Riggs
- Little Pancho: The Life of Tennis Legend Pancho Segura (2009), Caroline Seebohm, University of Nebraska Press, London and Lincoln, Nebraska, ISBN 978-0-8032-2041-6
- Tennis: Myth and Method, (1978) Ellsworth Vines and Gene Vier, Viking Press, New York