The 26th United States Congress was a meeting of the legislative branch of the United States federal government, consisting of the United States Senate and the United States House of Representatives. It met in Washington, D.C., from March 4, 1839, to March 4, 1841, during the third and fourth years of Martin Van Buren's presidency. The apportionment of seats in the House of Representatives was based on the 1830 United States census. Both chambers had a Democratic majority.

This list is arranged by chamber, then by state. Senators are listed by class, and representatives are listed by district.

Senators were elected by the state legislatures every two years, with one-third beginning new six-year terms with each Congress. Preceding the names in the list below are Senate class numbers, which indicate the cycle of their election. In this Congress, Class 1 meant their term began with this Congress, requiring reelection in 1844; Class 2 meant their term ended with this Congress, requiring reelection in 1840; and Class 3 meant their term began in the last Congress, requiring reelection in 1842.

The names of representatives are preceded by their district numbers.

The count below reflects changes from the beginning of the first session of this Congress.

Lists of committees and their party leaders.