Leon

The club was created from an application by Unión de Curtidores which merged with Selección de Guanajuato. With the money raised, the directive hired Marcial Ortiz, Raul Varela, Alfonso Montemayor, Salvador Ramírez, Conrado Muniz, Vicente Serrano, Pepe Cortes, "Sticks" Ramírez, Elpidio Sánchez, and Joaquín Source Duillo Dobles. It participated in the Liga Mayor's second season (1944–45). The team comprised Argentinian players and Miguel Rugilo that served as coach and goalkeeper holder. Battaglia played defense plus two fronts; Marcos Aurelio scored 14 goals with Ángel Fernández. The team debuted at Patria Stadium on August 20, 1944, against Atlante and lost by a score of 5–3.

In the 1945–46 season another team appeared in the city: the San Sebastián de León. They placed fourth out of 16 teams with 30 games, 17 wins, 4 draws, 9 losses for 38 points. Their top scorer, with 24 goals, Alberto Mendoza.

In the 1946–47 season notable players joined, one of whom was Adalberto Lopez, who scored 33 goals. In general, the team had a great campaign being runner-up with 41 points and maintained a fourteen-game winning streak. Another important element was Marcos Aurelio, who highlighted with 16 goals. A match against Atlante was scheduled place in Mexico City on June 1, 1947, in the Stadium Insurgentes (now Estadio Ciudad de los Deportes) which took place in León, but had to switch venues due to an epidemic of foot-and-mouth disease afflicting the Bajío region

In a match against Club America on May 9, 1946, Florencio Caffaratti accidentally touched an electrical wire after scoring a goal. Alfonso Montemayor rescued him. Subsequently, Caffaratti gave a gold coin to Montemayor with the inscription: "In appreciation of Montemayor by F. Caffaratti."

1947–48

When José María Casullo coached Club León, the greens lost seven times, three of them against Atlas Gold. The team tied at 36 points with the Jalisco Gold at first place. Jalisco Gold broke the tie with a score of 2–0.

1948–49

Club León defeated Asturias 2–0 with goals by Adalberto López to prevent a tie with Atlas and Guadalajara who remained a point, and Leon became the first to win the tournament campeonísimo cup after defeating Atlante 3–0 on August 14, 1949.

1951–52

Club León switched coaches to Antonio López Herranz. Antonio Carbajal joined the team with the return of Marcos Aurelio, Sergio Bravo, and Saturnino Martínez. The team played against a Guadalajara team coached by José María Casullo. León won both games of the year with scores of 1–0. In the penultimate round, León lost to Guadalajara by 1 point.

In the following season, the team remained in third place at 27 points. For the 1953–54 season it finished eighth with 21 points.

1955–56

The season's roster increased to 14 teams. León won the best streak in club history with 12 wins and 7 draws before losing against Tampico (1–0). The final game was played at the University Olympic Stadium Mexico City, where León defeated Oro (4–2) and Toluca.

In 1956–57 León lost to Guadalajara. In 1957–58 they reached fifth place but won the Cup title.

1960s

León remained in fifth place in the 1960–61 season with 26 points, fifth place in 1961–62 with 25 points, ninth place in 1962–63 with 25 points, ninth place in 1963–64 with 25 points, seventh place in 1964–65 with 30 points, ninth place in 1965–66 with 28 points, fifth place in 1966–67 with 34 points, fifth place in 1967–68 with 35 points, seventh place in 1968–69 with 31 points, and seventh place in 1969–70 with 31 points and when Hugo Sanchez join club leon they won the apertura 1975 si club leon was the best team back in the days on the 70s and late 80s.

1970s

For the Mexico 70 Tourney, there were two technical changes: the starter Argentine Luis Grill was replaced, but was reinstated after Antonio Carbajal left, as a result, left with 33 points to fourth overall Sergio Anaya new stand becomes scorer the contest with 16 touchdowns, while Luis Estrada mark 13 goals. 1970–71 players arrive, Jorge Davino, Roberto Salomone and Juan Valiente who scored ten goals, the club was led by Carbajal and ranked fourth with 38 points.

In 1972–73, initiate driven A. Carbajal was replaced by Rafael Albrecht that served as player and coach. The final game was against Cruz Azul.

In 1973–74 the team failed to qualify at fifth place with 40 points.

First relegation

In 1986–87 Jorge Davino scored 10 points in 19 days and start the 31 day leon when back to second division and they appear back on first division on May 10, 2012 and they won the Apertura when they arrived to first division.

1990s

The Esmeraldas returned to the Primera División for the 1990–91 season and were coached by Victor Manuel Vucetich, who debuted in the top flight and led the entire tournament. He led the club in sixth place with 41 points but did not qualify to be third in group 3, and Martin Uribe Francisco Peña highlighted with 13 and 12 goals.

Second relegation

Robert Zermeno cost the team and landed them in last place with 19 points.

After relegation, the club was sold to Argentine businessman Carlos Ahumada.

On 19 November 2010, Grupo Pachuca purchased the club.

Return to Primera División

Argentine Gustavo Matosas began leading León on 7 January 2012, after being hired in September 2011. During the Apertura 2011 campaign, he could not have a presence off the bench or be registered as coach because he had coached Querétaro FC in the same tournament. Matosas' 10 wins, 4 draws, and 0 defeats in 14 regular season fixtures, resulted in an ERA of 70.83% and the overall leader, helping them earn a direct qualification to semi-finals of the play-offs. In the semi-finals, they faced Correcaminos UAT and won 1–0 in the second match before facing the Lobos BUAP in the final, winning by an aggregate score of 7–3 and the right to play again in the Promotional Final. Facing 2011 Apertura championship winners Correcaminos UAT, León won by an aggregate score of 6–2, thus returning to the Mexican top-flight for the 2012–13 season. León had struggled for their fourth final for promotion after losing against Irapuato in 2003, Dorados de Sinaloa in 2005, and Indios de Ciudad Juárez in 2008.

León won both tournaments (the Apertura and Clausura) of the 2013–14 season and became the first team in Mexico's history to win two consecutive championship titles twice — winning the first of these during the 1947–48 and 1948–49 leagues consecutively.

Matosas and León parted ways after failing to make it to the 2014 Apertura championship stage. Argentine Juan Antonio Pizzi was named as his replacement.

On 31 January 2016, following a 3–1 away loss to Tigres UANL, Pizzi left the charge to join Chile as their new manager and was subsequently replaced by Luis Fernando Tena. The club managed to reach the semi-final stage of the Clausura championship, losing out to sibling club and eventual winners C.F. Pachuca with an aggregate score of 3–2.

Following a lackluster beginning to the 2016 Apertura where León summed up 4 points within 7 league matches, Tena was let go and Argentina Javier Torrente was brought in. Regardless of the uninspiring start, the club managed to reach the championship stage, losing to eventual winners Tigres UANL in the semi-finals by an aggregate score of 3–1.

In August 2017, Torrente was let go after a year as manager and was replaced by Gustavo Díaz.

On 18 September 2018, Ignacio Ambríz was named manager of León, replacing Díaz. During the 2019 Clausura, he helped León attain the records of most consecutive wins with eleven and the most points attained during the 17-match tournament format (41 points). They faced Tigres UANL in the Clausura championship final but lost following an aggregate score of 1–0. Regardless, Ambríz's feats with the club contributed to him being named best manager at the conclusion of the season.

After a first place finish with 40 points in the Guardianes 2020 general table, on 13 December, León won the league title defeating Club Universidad Nacional with an aggregate score of 3–1, becoming Mexico's joint fourth most successful team with eight titles in total alongside Cruz Azul.