| Challenger Liuzhou | 10/22 02:00 | 24 | [262] Ji Sung Nam v Kaichi Uchida [284] | 6-3,7-6 | |
| Challenger Ningbo | 10/17 04:55 | 26 | [275] Ji Sung Nam v Bradley Klahn [104] | 6-7,6-7 | |
| Challenger Ningbo | 10/16 03:35 | 25 | [186] Andrew Harris v Ji Sung Nam [275] | 3-6,5-7 | |
| Challenger Ningbo | 10/14 08:25 | 24 | Ji Sung Nam v Shuichi Sekiguchi | 6-1,6-1 | |
| Challenger Kaohsiung | 09/20 06:50 | 27 | [300] Ji Sung Nam v Marc Polmans [158] | 6-3,1-6,4-6 | |
| Challenger Kaohsiung | 09/19 03:00 | 26 | [300] Ji Sung Nam v Andrew Harris [189] | 6-2,6-2 | |
| Challenger Kaohsiung | 09/18 03:30 | 25 | Chang-Lin Tsai v Ji Sung Nam | 4-6,1-6 | |
| Challenger Kaohsiung | 09/17 02:50 | 24 | Ji Sung Nam v Cheng-Yu Yu | Retired | |
| Davis Cup | 09/15 06:35 | - | Zhizhen Zhang v Ji Sung Nam | Cancelled | |
| Davis Cup | 09/14 04:50 | - | [210] Zhe Li v Ji Sung Nam [301] | 6-7,6-7 | |
| Challenger Jinan | 09/03 04:45 | 24 | [358] Ivan Nedelko v Ji Sung Nam [298] | 4-6,7-5,6-3 | |
| Challenger Baotou | 08/29 02:00 | 26 | [298] Ji Sung Nam v Yan Bai [222] | 3-6,6-4,5-7 | |
| Challenger Baotou | 08/27 05:40 | 25 | [298] Ji Sung Nam v Arjun Kadhe [160] | 6-3,6-3 | |
| Challenger Yokkaichi | 08/09 04:30 | 27 | Sho Shimabukuro v Ji Sung Nam | 6-7,6-3,6-2 | |
| Challenger Yokkaichi | 08/08 03:20 | 26 | [255] Ji Sung Nam v Hiroki Moriya [215] | 6-2,5-7,7-6 | |
| Challenger Yokkaichi | 08/06 04:35 | 25 | Ji Sung Nam v Jumpei Yamasaki | 6-3,6-2 | |
| Challenger Chengdu | 08/02 04:00 | 27 | [292] Ji Sung Nam v Hyeon Chung [166] | 6-7,6-1,3-6 | |
| Challenger Chengdu | 08/01 03:00 | 26 | [475] Dayne Kelly v Ji Sung Nam [292] | 6-7,3-6 | |
| Challenger Chengdu | 07/31 03:50 | 25 | [88] Mao-Xin Gong v Ji Sung Nam [292] | 6-7,1-6 | |
| Challenger Nur-Sultan | 07/18 06:50 | 26 | [126] Evgeny Donskoy v Ji Sung Nam [297] | 3-6,6-1,6-4 | |
| Challenger Nur-Sultan | 07/16 08:25 | 25 | [399] Teymuraz Gabashvili v Ji Sung Nam [297] | 6-1,4-6,2-6 | |
| ITF M15 Almaty | 07/12 04:00 | 27 | Ji Sung Nam v Andrey Golubev | 3-6,3-6 | |
| ITF M15 Almaty | 07/11 04:00 | 26 | Ji Sung Nam v Sagadat Ayap | 6-1,3-6,6-1 | |
| ITF M15 Almaty | 07/09 07:30 | 25 | Ji Sung Nam v Sultan Narbekov | 6-1,6-1 | |
| Challenger Columbus | 06/16 17:55 | 29 | [349] Ji Sung Nam v Mikael Torpegaard [214] | 1-6,5-7 | |
| Challenger Columbus | 06/15 15:00 | 28 | [349] Ji Sung Nam v Dudi Sela [164] | Retired | |
| Challenger Columbus | 06/14 17:00 | 27 | [349] Ji Sung Nam v Zhizhen Zhang [320] | 6-3,6-2 | |
| Challenger Columbus | 06/13 21:35 | 26 | [397] Alejandro Gonzalez v Ji Sung Nam [349] | 4-6,2-6 | |
| Challenger Columbus | 06/12 16:10 | 25 | [349] Ji Sung Nam v Jeffrey John Wolf [269] | 6-4,3-6,6-4 | |
| Challenger Columbus | 06/10 22:45 | 24 | Cannon Kingsley v Ji Sung Nam | 5-7,4-6 |
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.