| Office: | Judge of the United States District Court for the District of New Hampshire |
| Term Start: | July 27, 1866 |
| Term End: | January 2, 1891 |
| Appointer: | Andrew Johnson |
| Predecessor: | Matthew Harvey |
| Successor: | Edgar Aldrich |
| Office1: | President pro tempore of the United States Senate |
| Term Start1: | April 26, 1864 |
| Term End1: | February 19, 1865 |
| Predecessor1: | Solomon Foot |
| Successor1: | Lafayette S. Foster |
| Jr/Sr2: | United States Senator |
| State2: | New Hampshire |
| Term Start2: | June 27, 1857 |
| Term End2: | July 27, 1866 |
| Predecessor2: | James Bell |
| Successor2: | George G. Fogg |
| Office3: | Member of the New Hampshire House of Representatives |
| Term3: | 1842-1843 1846 1854-1855 |
| Birth Date: | 24 October 1809 |
| Birth Place: | Stratham, New Hampshire, US |
| Death Place: | Manchester, New Hampshire, US |
| Party: | Republican |
| Education: | Dartmouth College read law |
Daniel Clark (October 24, 1809 – January 2, 1891) was a United States senator from New Hampshire and a United States district judge of the United States District Court for the District of New Hampshire.
Born on October 24, 1809, in Stratham, New Hampshire, Clark attended the common schools Hampton Academy (now New Hampton School) and Union College in Schenectady, New York. He graduated from Dartmouth College in 1834 and read law in 1836. He was admitted to the bar and entered private practice in Epping, New Hampshire from 1836 to 1839. He continued private practice in Manchester, New Hampshire from 1839 to 1842, 1844 to 1846, and from 1847 to 1861. He was a member of the New Hampshire House of Representatives from 1842 to 1843, in 1846, and from 1854 to 1855.
Clark was elected as a Republican to the United States Senate to fill the vacancy caused by the death of United States Senator James Bell. He was reelected in 1861, and served from June 27, 1857, to July 27, 1866, when he resigned to accept a federal judicial post. He served as President pro tempore of the United States Senate during the 38th United States Congress. He was Chairman of the United States Senate Committee on Claims for the 37th through the 39th United States Congress.
Clark was nominated by President Andrew Johnson on July 27, 1866, to a seat on the United States District Court for the District of New Hampshire vacated by Judge Matthew Harvey. He was confirmed by the United States Senate on July 27, 1866, and received his commission the same day. His service terminated on January 2, 1891, due to his death in Manchester.
Clark was President of the New Hampshire constitutional convention in 1876.