London

The team's life began in 1950 at the Jr. B level with the London Lou Ball Juniors, playing in The 'Big 10' Western Division out of the Ontario Arena at the Western Fairgrounds. The team's namesake was Lou Ball Clothes, which were a chain of three stores owned by Lou Ball, coach of the team. They then proceeded to win the championship in 1952. The team was renamed to the London Collinson Flyers during the 1955–56 season before reverting to Lou Ball Juniors for 2 more seasons. In 1956 the 'Big 10' was divided, and London became a member of the Western Ontario Junior "B" Hockey League. The name changed to London Diamonds in 1958, then to the London Athletics in 1960. In 1961, the team was again renamed, being called the Nationals, after their sponsor, the Canadian National Recreation Association, an organization of employees of the Canadian National Railways.

In 1963 the Toronto Maple Leafs began sponsoring the Nationals. The Maple Leafs traditionally had affiliations with the Toronto Marlboros and St. Michael's Majors, however with the withdrawal of the Majors from the OHA, and the collapse of the Metro Junior A League, the Leafs were left with only one team. They decided to sponsor the junior team in London, which they wanted to play at the new London Gardens and be promoted to the Ontario Hockey Association.

The OHA initially balked at the proposition however, and so the Nationals continued to play in the Junior B league, winning the London Free Press Trophy as league champions in 1964 and 1965. For the 1965–66 season, the team was finally admitted to major junior hockey, and London's Junior B franchise moved to Ingersoll to make room for the Junior A Nationals. The team wore a uniform very similar to the Maple Leafs.

After three seasons, in 1968, direct NHL sponsorship of junior teams ended. The team and arena was sold to businessman Howard Darwin (he also owned the Ottawa 67's) for $500,000, who held a contest to rename the team, which the name "Knights" won, and changed the colours to green and gold.

In 1986, Howard Darwin sold the Knights and the arena to Paris, Ontario businessmen Jack Robillard, Al Martin and Bob Willson.

In 1994 the Knights were sold to St. Thomas, Ontario, real estate developer Doug Tarry Sr. He died before the team had played a game under his ownership, and the team was inherited by his son, Doug Tarry Jr. Upon taking command, Tarry carried out further renovations on the Gardens including a name change to the "London Ice House." He also alienated a fair portion of the team's fan base by changing the team's colours from green, gold and black to eggplant and teal, and changing the logo to a cartoon logo instantly and derisively nicknamed "Spiderknight".

In 2000, former NHL players Dale Hunter, Mark Hunter, and Basil McRae bought the Knights from Doug Tarry Jr.

The 2003–04 OHL season would mark the beginning of a remarkable dynasty. The Knights had the best regular season record in the CHL and set an OHL record with 110 points, but lost the OHL Western Conference final to the Guelph Storm. In the 2004–05 season, the Knights set a new CHL record by going 31 games in a row without a loss (29–0–2). The Knights finished the season with 120 points (59 wins, 7 losses, 2 ties), breaking their own OHL record set the previous season. In the playoffs, the Knights started by sweeping two best-of-seven series against the Guelph Storm and Windsor Spitfires. In the Western Conference final, the Knights defeated the Kitchener Rangers 4–1 to win the Wayne Gretzky Trophy. In the OHL finals against the Ottawa 67's, the Knights won the series 4–1 to win their first J. Ross Robertson Cup, ending the longest championship drought in the CHL. The London Knights qualified for the 2005 Memorial Cup both as OHL Champion and the tournament host. In the tournament round robin, they defeated the Rimouski Océanic 4–3, the Kelowna Rockets 4–2, and the Ottawa 67's 5–2. This earned the Knights a bye into the championship game in which they defeated Rimouski 4–0 to win their first Memorial Cup. In 2018, the 2004–05 London Knights were named the CHL's "Team of the Century".

Dale Hunter announced on May 14, 2012, he would not return to coach the Capitals in the 2012–13 season, choosing instead to return to the London Knights.

The Knights capped their OHL season with a game seven win over the Barrie Colts as Bo Horvat scored the game-winning goal in the last second of the third period to capture the Knights' second consecutive J. Ross Robertson Cup.

London finished the 2013–14 season third in the OHL with 103 regular season points. However, the only two teams above them were their division opponents, the Guelph Storm and Erie Otters, thus denying the Knights a third straight division title. After sweeping the Windsor Spitfires in the first round the Knights were eliminated by the Storm in five games. Nevertheless, the Knights earned a berth in the 2014 Memorial Cup, their third straight, by virtue of being selected to host the tournament the day after winning the OHL championship the year before.

On October 21, 2014, Mark Hunter resigned as Knights general manager after being appointed director of player personnel for the Toronto Maple Leafs.

The Knights entered the 2016 Memorial Cup as favourites due to their impressive winning streak and did not disappoint, dominating the round robin and outscoring their opponents by a combined score of 20–5. In the championship game, the Knights faced off against the CHL number-one ranked Rouyn-Noranda Huskies. The Huskies pushed the Knights to the limit, carrying a 2–1 lead late into the third period before Christian Dvorak scored with 4:11 remaining to force overtime, where a goal by Matthew Tkachuk earned the Knights their 17th-straight win and second Memorial Cup championship.

On July 6, 2016, McRae stepped down as general manager of the London Knights to become the director of player personnel for the Columbus Blue Jackets. He was replaced by former assistant general manager and former assistant coach of the London Knights, Rob Simpson.

The Knights subsequently finished the 2016–17 OHL season third in the Midwest. In the playoffs, they defeated the Windsor Spitfires in seven games before falling to the Erie Otters in seven games in the second round.

Having resigned from his role with the Toronto Maple Leafs, Mark Hunter returned as general manager of the London Knights on August 10, 2018, with Rob Simpson returning to his former role as assistant general manager.

The Knights played at the 2024 Memorial Cup in Saginaw, Michigan, after winning the J. Ross Robertson Cup that season. London lost to the host Saginaw Spirit by a 4–3 score in the final game. In 2025, the Knights won the J. Ross Robertson Cup, and defeated the Medicine Hat Tigers 4–1 in the final, to win their third Memorial Cup title.