| Liu Siyu | |
| Native Name: | 刘思宇 |
| Native Name Lang: | zh |
| Birth Date: | 1995 11, df=yes |
| Height: | 1.91m (06.27feet) |
| Careerprizemoney: | $18,440 |
| Singlesrecord: | 0–0 (at ATP Tour level, Grand Slam level, and in Davis Cup) |
| Singlestitles: | 0 |
| Highestsinglesranking: | No. 906 (11 October 2014) |
| Doublesrecord: | 0–1 (at ATP Tour level, Grand Slam level, and in Davis Cup) |
| Doublestitles: | 0 |
| Highestdoublesranking: | No. 1076 (9 August 2014) |
| Updated: | 1 May 2017 |
Liu Siyu (born 1 November 1995) is a Chinese tennis player.
Liu has a career high ATP singles ranking of 906 achieved on 11 October 2014. He also has a career high ATP doubles ranking of 1076 achieved on 9 August 2014.
Liu made his ATP main draw debut at the 2014 China Open in the doubles draw partnering Ning Yuqing.