Sishui County (simplified Chinese: 泗水县; traditional Chinese: 泗水縣; pinyin: Sìshuǐ Xiàn) is a county of southwestern Shandong province, People's Republic of China.

It is the easternmost county-level division of Jining City.

It takes its name from the Si River, which flows through the county.

The population was 590,326 in 1999.

[1] As 2012, this county is divided to 2 subdistricts, 8 towns and 3 townships.