| Challenger Kaohsiung | 07/15 07:40 | 25 | Nam, Ji Sung v Sugita, Yuichi | 4-6,2-6 | |
| ITF Korea F1 Qual | 05/02 02:00 | - | Cho, Min Hyeok v Nam, Ji Sung | 6-4,6-7,6-2 | |
| ITF Korea F1 Qual | 05/01 03:00 | - | Kim, Cheong-Eui v Nam, Ji Sung | 1-6,7-5,2-6 | |
| ITF Korea F1 Qual | 04/30 01:00 | - | Nam, Ji Sung v Hong, Seong Chan | 6-0,6-2 | |
| ITF Korea F1 | 04/25 03:00 | - | Chung, Hyeon v Nam, Ji Sung | 6-0,6-0 | |
| ITF Korea F1 | 04/24 01:00 | - | Nam, Ji Sung v Na, Jung-Woong | 7-5,6-2 | |
| ITF Korea F1 | 04/22 01:00 | - | Nam, Ji Sung v Nam, Hyun Woo | Retired | |
| ITF China F3 | 03/19 02:00 | - | Nam, Ji Sung v Gao, Xin | Retired | |
| ITF China F2 | 03/13 04:00 | - | Zhang, Ze v Nam, Ji Sung | 2-6,6-2,6-2 | |
| ITF China F2 | 03/12 04:40 | - | Ouyang, Bowen v Nam, Ji Sung | 1-6,6-7 | |
| ITF China F1 | 03/06 02:00 | - | Nam, Ji Sung v Yan Bai | 6-3,3-6,4-6 |
Nam Ji-sung (born 15 August 1993) is a South Korean tennis player. He has a career high ATP singles ranking of world No. 236 achieved on 12 August 2019. He also has a career high ATP doubles ranking of No. 102 achieved on 3 February 2020.
Playing for South Korea in Davis Cup, Nam has a W/L record of 3–7.