| Kook Hae-seong | |
| Position: | Outfielder |
| Birth Date: | 8 October 1989 |
| Birth Place: | Gunsan, South Korea |
| Bats: | Switch |
| Throws: | Right |
| Debutleague: | KBO |
| Debutdate: | June 23 |
| Debutyear: | 2012 |
| Debutteam: | Doosan Bears |
| Finalleague: | KBO |
| Finaldate: | September 29 |
| Finalyear: | 2023 |
| Finalteam: | Lotte Giants |
| Statleague: | KBO |
| Stat1label: | Batting average |
| Stat1value: | .238 |
| Stat2label: | Home runs |
| Stat2value: | 11 |
| Stat3label: | Runs batted in |
| Stat3value: | 67 |
| Teams: |
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Kook Hae-seong (; born 8 October 1989) is a South Korean professional baseball outfielder who played for the Doosan Bears of the KBO League. His major position is right fielder and left fielder, but he sometimes plays as center fielder or first baseman. He graduated from .[1] Upon graduation from high school, he made himself eligible for the 2008 KBO First-Year Player Draft, but went undrafted. Instead, Kook signed a contract with the Chicago Cubs in 2007. However, after the problem of elbow was found and the contract was broken, he was signed by the Doosan Bears as an undrafted free agent.[2]