The Southern Caucus was a Congressional caucus of Southern Democrats in the United States Senate chaired by Richard Russell, which was an effective opposition to civil rights legislation and formed a vital part of the later conservative coalition that dominated the Senate into the 1960s.

The Caucus was still active in 1964 when they tried and failed to derail the 1964 Civil Rights Act.

The caucus was particularly interested in stopping federal legislation on Civil rights. The tone of the Southern Caucus was to be more moderate and reasonable so as not to alienate potential allies and to eschew the explicit white supremacism of Senators such as Tom Connally.

The group first emerged as a more formal group in a successful filibuster that blocked the Anti-Lynching Bill of 1937. This had passed the House of Representatives and seemed to have majority support in the Senate. This was at the same time as other elements of President Franklin Roosevelt's legislative program were meeting legislative obstacles thanks to the growth of a loose conservative coalition within Congress of Republicans as well as various more conservative sections of the Democratic Party.

During and after the Second World War the Southern Caucus widened its tactics from pure obstruction through the filibuster to courting of Northern allies and a rearguard approach of allowing some bills through and amending others to an acceptable form.

William White's book Citadel was credited as the first expose of the Southern Caucus's control over the senate, in which it described the caucus as "for all the world like the reunions of a large and highly individualistic family whose members are nevertheless bound by the one bond". The book argued that the caucus was quite wide-ranging in its views on economics or foreign policy, but that its protection of the filibuster and general devotion to States rights meant that they rejected the Tennessee Senator Estes Kefauver.

The root of the group's power lay in the one-party nature of the Solid South which meant that there was little turnover of Senators from the region, coupled with the seniority system within the Senate which meant that power would accrue to Senators with particularly long service. This was particularly the case when the Democrats controlled the Senate and therefore the Committee chairmanships.

The Senate's rules, which mean that in general Senators once recognized can speak for as long as they wish, meant that bills that had support from other branches of the government, and even from the majority of Senators, could be held up for a very long time by a determined minority – and, importantly, cause unacceptable delays in other business. This device, the filibuster, was used effectively by the Southern Caucus to deny a number of civil rights Bills passage into law.