The Marines franchise began in 1950 as the Mainichi Orions, an inaugural member of the Pacific League. The Marines won the inaugural Japan Series in 1950. In 1958, the team was merged with the Daiei Unions and renamed the Daimai Orions. In 1964 they became the Tokyo Orions, and the Lotte Orions in 1969. The franchise was slow to replicate its initial success: the Orions made the Japan Series in 1960 and 1970, only to lose both years. The team played in central Tokyo until 1972. From 1973 to 1977 the Lotte Orions played in the northern Japanese city ofSendai. In 1974, they beat the Chunichi Dragons, becoming the first Pacific League team to win the Series in ten years as the Yomiuri Giants had claimed the prior nine titles behind the Oh–Nagashima attack. In 1978 the team returned to the Tokyo area, settling in Kawasaki's Kawasaki Stadium, at one time home to the Taiyo Whales. In 1992, the team moved to Chiba City's Chiba Marine Stadium on the eastern shore of Tokyo Bay and were renamed the Chiba Lotte Marines. The team failed to reach the Japan Series again until 2005. The Marines started the 2005 season in first place behind American manager Bobby Valentine, but fell behind the Fukuoka SoftBank Hawks as the year progressed. Under the playoff format of the time, the preliminary five-game playoff round, prior to the Japan Series, saw the teams with the best first and second half records face off. The Marines defeated the Hawks three games to two in the Pacific League championship, winning the rubber match despite entering the eighth inning trailing, 2–1. The Marines thus qualified for the Japan Series, the first time they had reached the tournament since 1974, a 31-year drought. In a one-sided series, the Marines swept the Hanshin Tigers in four games, scoring ten runs in each of the first three games. The apparent ease with which the Marines defeated the Tigers added fuel to the ongoing debate concerning the need for a playoff system in the Central League, which was finally added in 2007. The Marines went on to defeat South Korea's Samsung Lions in the final round of the Konami Cup Championships. In 2010, the Marines clinched third place on the last day of the season to earn a berth into the Climax Series. They went on to become the first third place team to ever win the Climax Series, and faced off with the Chunichi Dragons in the 2010 Japan Series. The Marines defeated the Dragons in seven games, composed of four wins, two losses, and one tie, winning their second Japan Series in under ten years.
26 – This number was retired in honor of the Marines' fans in 2005. It was inspired by some teams in other sports.The Tohoku Rakuten Golden Eagles has the No. 10 retired in similar fashion. MLB's Los Angeles Angels has retired No. 26, in same fashion, for the founder Gene Autry.
Mar-kun is a main mascot character of the Marines. With his girlfriend Rine-chan and his young brother Zu-chan. he entertains spectators at team games. Their name is a separateness of the team name. Mysterious fish is a new mascot character since May 2017. He is a weird fish with legs. He has collaborated with Hawaiian Airlines that former Marines' player Benny Agbayani works for, since 2018.
