Kaohsiung Metro is a rapid transit and light rail system servicing the city of Kaohsiung. Kaohsiung Metro currently has two rapid transit lines and one light rail line, with another rapid transit line being built and is expected to be finished by 2028. Kaohsiung Metro opened for service on March 9, 2008.

Red line (rapid transit)
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The Red line was the first rapid transit line of Kaohsiung Metro. However, not all parts of the Red line opened at one time. In fact, some parts are still being built and are not finished yet. The history of the service of the Red line is as follows:

* March 9, 2008: The part from Siaogang to Ciaotou Station opened for service. However, Formosa Boulevard was not finished at the time so trains did not stop at Formosa Boulevard.
* September 14, 2008: Formosa Boulevard is opened for service, connecting with the Orange line.
* December 23, 2012: The Red line extends north from Ciaotou Station to Gangshan South.
* *2027:* The Red line is expected to be extended north from Gangshan South to Lujhu South, adding six new stations to the Red line, bringing the total number of stations on the Red line to 30.

After all parts of the Red line are finished, the Red line will become a 37.64 km rapid transit line running from Siaogang in southern Kaohsiung to Lujhu South in northern Kaohsiung. The part from Siaogang to Zuoying is underground, the parts from World Games to Ciaotou Station and from Gangshan to Lujhu South are elevated, and Gangshan South is at ground level.

Orange line (rapid transit)
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The Orange line was the second rapid transit line of Kaohsiung Metro. The Orange line opened on September 14, 2008, and is 14.4 km long with 14 stations running from Sizihwan in western Kaohsiung to Daliao in eastern Kaohsiung. All metro stations on the Orange line are underground except for Daliao, which is at ground level.

Yellow line (rapid transit)
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The Yellow line has not been finished yet, but it will become the third rapid transit line of Kaohsiung Metro once it opens for service. The Yellow line is expected to open by 2028, and will be 22.91 km long with 23 stations. The line will run through Kaohsiung's Niaosong District, dividing into two branches near Chengcing Lake: one towards Cruise Terminal and the other towards Cianjhen Senior High School. The Yellow line will use a medium-capacity rail system and will be mostly underground.

Circular light rail
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The Circular light rail is the only light rail line of Kaohsiung Metro. However, not all parts of the Circular light rail opened at one time. In fact, some parts are still being built and are not finished yet. The history of the service of the Circular light rail is as follows:

* October 16, 2015: The part from Lizihnei to Kaisyuan Jhonghua opened for service.
* June 26, 2016: The Circular light rail is extended from Kaisyuan Jhonghua to Kaohsiung Exhibition Center.
* June 30, 2017: The Circular light rail is extended from Kaohsiung Exhibition Center to Dayi Pier-2.
* September 26, 2017: The Circular light rail is extended from Dayi Pier-2 to Hamasen.
* January 12, 2021: The Circular light rail is extended from Hamasen to Gushan District Office and from Lizihnei to Kaisyuan Park.
* December 16, 2021: The Circular light rail is extended from Gushan District Office to Museum of Fine Arts railway station.
* October 5, 2022: The Circular light rail is extended from Museum of Fine Arts railway station to Heart of Love River.
* *2023:* The Circular light rail is expected to be extended from Heart of Love River back to Kaisyuan Park, making the Circular light rail a real loop and bringing the total number of stations to 38.

After all parts of the Circular light rail are finished, the Circular light rail will become a 22.1 km light rail loop line servicing Central Kaohsiung. All light rail stations are at ground level except for Love Pier, which is an elevated light rail station.