The Federal Assembly (Czech: Federální shromáždění, Slovak: Federálne zhromaždenie) was the highest organ of state power of Czechoslovakia from 1 January 1969 until the amendment of the state constitution on 23 April 1990. From 23 April 1990 until the dissolution of Czechoslovakia on 31 December 1992, it functioned as the state's federal legislature.

Chapter 3 of the 1960 Constitution of Czechoslovakia recognized it as "the supreme organ of state power and the sole statewide legislative body."

The Federal Assembly was divided into two equal chambers, the Chamber of People (Sněmovna lidu; other translation House of People) and the Chamber of Nations (Sněmovna národů; other translation House of Nations). Following the Velvet revolution, proposals were made to rename the two chambers into the Chamber of Deputies (Poslanecká sněmovna) and the Senate (Senát) respectively, restoring the chamber names used during the Interwar period. An alternative proposal suggested transforming the Chamber of People into a unicameral Federal Assembly, and replacing the Chamber of Nations with a Bundesrat-style Federal Council (Federální rada).

The Chamber of the People reflected a system of proportional representation: in 1992 it included 99 deputies from the Czech Socialist Republic and 51 deputies from the Slovak Socialist Republic. The Chamber of Nations had 150 members, 75 from each republic. Deputies were selected through popular elections and served five year terms of office; all members of both houses served concurrently. However, before the Velvet Revolution — and thus, in all but the last two assemblies — there was only one party to vote for, National Front, and it was impossible to give a preferential vote.

The Post-Velvet Revolution electoral law, used to elect the last two assemblies, provided that both houses of the Federal Assembly would be elected by party-list proportional representation in multi-member electoral districts which correspond to the regions of each Republic. Seats for each Republic were allocated among its electoral districts on the basis of the votes actually cast in each. Voters must choose only one political party to vote for, but they may use up to four preferential votes for particular candidates of that party, which affect the final order of the candidates on the party list. To obtain seats, a party was required to obtain at least 5% of the Republic-wide votes in either of the Republics. The allocation of seats was made in two stages – first, seats were allocated within each electoral district using the Hagenbach-Bischoff quota. The remainders were then used to allocate any seats left unfilled on a republic-wide basis, again using the Hagenbach-Bischoff quota.

After an election each chamber met to select its own Praesidium consisting of three to six members. Together, the chambers elected the forty-member Presidium of the Federal Assembly, which served as the legislative authority when the assembly was not in session. A joint session of the Federal Assembly selected its chairman and vice chairman.

The Federal Assembly met in regular session at least twice a year, in the spring and fall. Legislation presented to the assembly at these sessions had to be approved by both chambers and in some cases required a majority vote by both the Czech and the Slovak deputies in the Chamber of Nations.

Constitutionally, the Federal Assembly was vested with great lawmaking powers, and had exclusive jurisdiction in all matters of foreign policy, fundamental matters of domestic policy, the economic plan, and supervision of the executive branch of government.