The 19th 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, 1825, to March 4, 1827, during the first two years of John Quincy Adams's presidency. The apportionment of seats in the House of Representatives was based on the 1820 United States census. The Senate had a majority of Jackson Men, while the House had an Anti-Jackson (pro-Adams) majority.

The count below identifies party affiliations at the beginning of the first session of this congress. Changes resulting from subsequent replacements are shown below in the "Changes in membership" section.

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

(J) following a name means the member was of the Jackson faction. (A) that the person was a member of the Adams (anti-Jackson) faction.

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 ended with this Congress, facing re-election in 1826/1827; Class 2 meant their term began in the last Congress, facing re-election in 1828/1829; and Class 3 meant their term began in this Congress, facing re-election in 1830/1831.

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

Lists of committees and their party leaders.