| Ko Chang-seong | |
| Position: | Relief pitcher |
| Birth Date: | 21 December 1984 |
| Birth Place: | Seoul, South Korea |
| Bats: | Right |
| Throws: | Right |
| Debutleague: | KBO |
| Debutdate: | April 2 |
| Debutyear: | 2008 |
| Debutteam: | Doosan Bears |
| Finaldate: | October 13 |
| Finalyear: | 2018 |
| Finalteam: | kt wiz |
| Statleague: | KBO |
| Stat1label: | Win–loss record |
| Stat1value: | 18–13 |
| Stat2label: | Holds |
| Stat2value: | 62 |
| Stat3label: | Strikeouts |
| Stat3value: | 212 |
| Stat4label: | Earned run average |
| Stat4value: | 3.89 |
| Teams: |
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| Hangul: | 고창성 |
| Hanja: | 高昌成 |
| Rr: | Go Changseong |
| Mr: | Ko Ch'angsŏng |
Ko Chang-seong (; born December 21, 1984, in Seoul, South Korea) is a sidearm pitcher playing for the NC Dinos in the KBO League. He bats and throws right-handed.
Ko played college baseball at Kyungsung University in Busan. He was drafted by the Doosan Bears in the 3rd round (20th overall) of the Korea Baseball Organization Draft.
In the set-up role, Ko drew the attention of the league when he posted a 1.95 ERA and earned 16 holds in . He enjoyed another great season as a setup man in, when he earned 22 holds which was runner-up in the KBO league.[1] After the 2010 season, Ko was selected for the South Korean national baseball team to compete in the 2010 Asian Games where he won the gold medal.[2]
In, Ko earned 14 holds but his ERA rose to 4.44. In, he finished the season with an 8.62 ERA losing all ability to control his pitches. Ko was sent down to the second-tier team of the Bears in the middle of the 2012 season and traded to the NC Dinos after the season.