WASHINGTON — A panel of three federal judges threw out Alabama’s congressional map on Monday and ordered state lawmakers to draw a new one with two, rather than just one, districts that are likely to elect Black representatives.

The map that Alabama’s Republican-majority State Legislature adopted last fall drew one of the state’s seven congressional districts with a majority of Black voters. The court ruled that with Alabama’s Black population of 27 percent, the state must allot two districts with either Black majorities or “in which Black voters otherwise have an opportunity to elect a representative of their choice.”

“Black voters have less opportunity than other Alabamians to elect candidates of their choice to Congress,” the panel of judges wrote.

The case is certain to be appealed and could lead to the U.S. Supreme Court addressing the question of whether lawmakers can draw political maps to achieve a specific racial composition, a practice known as racial gerrymandering. In 2019, the Supreme Court ruled that federal courts have no role to play in blocking partisan gerrymanders. However, the court left intact parts of the Voting Rights Act that prohibit racial or ethnic gerrymandering.

If Alabama legislators do not produce and pass a new map with a second majority-Black district within 14 days, the court will appoint a special master to do so, the judges wrote. That second district would be a significant legal and political victory for Democrats, who would be overwhelming favorites to carry it.

“This decision is a win for Alabama’s Black voters, who have been denied equal representation for far too long,” said Eric H. Holder Jr., the chairman of the National Democratic Redistricting Committee. “The map’s dilution of the voting power of Alabama’s Black community — through the creation of just one majority-Black district while splitting other Black voters apart — was as evident as it was reprehensible.”

The Alabama Republican Party chairman, John Wahl, said he was disappointed in the court’s ruling and expected it to be appealed. “The basic outlines of Alabama’s congressional districts have remained the same for several decades and have been upheld numerous times,” he said. “What has changed between now and those past decisions to cause the court to act in this manner?”

The Alabama congressional map is the second drawn by Republicans to be struck down by courts this month. Two weeks ago, the Ohio Supreme Court invalidated a map drawn by Republicans which would have given the G.O.P. a likely 12-to-3 advantage in the state’s congressional delegation. North Carolina’s new congressional map is also enmeshed in a legal battle, and several other states are likely to be sued over their political cartography.

The three-judge panel is made up of two Federal District Court judges appointed by former President Donald J. Trump and one by former President Bill Clinton. All three signed the opinion. The panel pushed back Alabama’s ballot qualification deadline from Jan. 28 to Feb. 11 for the state’s May primaries.

Alabama’s secretary of state, John H. Merrill, declined to comment on the ruling.

Adam Kincaid, the executive director of the National Republican Redistricting Trust, the party’s main mapmaking organization, said the map was based on one that was cleared in 2011 by President Obama’s Justice Department, then led by Mr. Holder, and comports with the Voting Rights Act.

“The new map maintains the status quo,” Mr. Kincaid said. “It does not violate Section 2 of the V.R.A. under the current application of the law and should be upheld.”

For three decades, Alabama has had a single majority-Black congressional district that has elected Black Democrats. The state’s other six districts have been represented only by white Republicans since 2011.

In Alabama’s lone majority-Black district, represented by Terri Sewell, a Democrat, more than 60 percent of the voters are Black — representing almost a third of the state’s Black population. The bulk of the state’s remaining Black population is split — or “cracked” — among the First, Second and Third Congressional Districts, all of which have been safely Republican for years.

In 2018, a group of Black voters filed a federal lawsuit arguing that the Alabama map violated the Voting Rights Act. They lost.

“It’s past time for Alabama to move beyond its sordid history of racial discrimination at the polls, and to listen to and be responsive to the needs and concerns of voters of color,” Tish Gotell Faulks, the legal director of the A.C.L.U. of Alabama, said following Wednesday’s ruling.

President Biden and congressional Democrats sought to enact legislation that, among other things, would have limited partisan gerrymandering by state legislatures. That effort died when Senators Kyrsten Sinema of Arizona and Joe Manchin III of West Virginia, both Democrats, thwarted a party-wide push to overcome Republican opposition by changing Senate rules.

Nick Corasaniti contributed reporting.