Clark Jillson (1825–1894) was an American politician who served as the 18th Mayor of Worcester, Massachusetts, from 1873 to 1874.

[2] He came to Worcester in 1845, taking a job with Howe & Goddard at seventy-five cents a day.

He also wrote for newspapers and magazines, and was elected president of the Young Men's Rhetorical Society in 1853.

[4] He was the first mayor to use the veto power, and his administration saw the first reduction of city debt in thirteen years.

[3][2] Jillson was a founding member of the Sons and Daughters of Vermont, and served as president of Worcester Society of Antiquity.