David Letterman marched back into the Ed Sullivan Theater on Thursday night and unloaded on CBS over its decision to cancel Stephen Colbert’s late-night show — before helping toss couches, watermelons and a wedding cake off the roof of the landmark Manhattan venue.

The former “Late Show” host joined Colbert for a blistering on-air segment that mocked the network and its new ownership just days before Colbert’s final broadcast.

At the conclusion of the segment, the outgoing host asked Letterman if he wanted to offer some parting words to viewers.

Letterman took the opportunity to address CBS, instead, saying: “To the folks at CBS, in the words of the great Edward R. Murrow, good night and good luck, motherf–kers.”

The now-retired late-night legend paid homage to Colbert while drawing loud applause from the studio audience.

“Well, you know what happened backstage? I’m standing backstage, a guy comes over, he says he’s from CBS and he fires me,” Letterman joked after walking onstage to a lengthy standing ovation.

“What is going on over there?!”

Letterman, who launched “The Late Show” in 1993 and hosted it for more than two decades before passing the baton to Colbert, made clear he was still furious over the network’s handling of the franchise.

“I have every right to be pissed off, so I’ll be pissed off here a little bit,” Letterman said.

The appearance quickly shifted to a stunt aimed squarely at CBS.

After Letterman asked whether the network owned the furniture on the set, crew members hauled couches and props to the roof of the Ed Sullivan Theater, where they were hurled onto a giant CBS logo in what the pair described as the “wanton destruction of CBS property.”

Letterman also sent Colbert’s desk chair flying off the building, along with watermelons and a wedding cake.

CBS’ decision last summer to pull the plug on “The Late Show with Stephen Colbert” after an 11-year run stunned the entertainment world.

The move came as Skydance Media was merging with CBS parent company Paramount Global, but CBS insisted the decision was purely an economic one, saying Colbert’s show was losing $40 million a year.

Critics including Letterman and fellow late-night host Jimmy Kimmel vociferously questioned that explanation, pointing to Colbert’s penchant for Trump-bashing as the merger required federal approval.

President Trump celebrated Colbert’s cancellation on Truth Social, writing that he “absolutely love[d] that Colbert got fired” while saying the comedian had less “talent” than his ratings.

Letterman has repeatedly accused CBS executives of hiding behind corporate talking points while dismantling one of the network’s signature programs.

Earlier this month, he blasted the company’s owners as “lying weasels” and suggested the financial rationale surrounding Colbert’s ouster was far from the full story.

He has also defended Colbert personally, praising the host for what he called a “masterful job” confronting political issues on air while arguing executives were ignoring the broader cultural impact of gutting late-night television.

During Thursday’s appearance, Letterman mixed anger with nostalgia as he reflected on the Ed Sullivan Theater, which housed “The Late Show” franchise for more than three decades.

“This theater, you folks wouldn’t be in this theater if it weren’t for me, and Stephen wouldn’t be here if it weren’t for me,” Letterman said.

He went on to lament that Colbert’s run had “come to a screeching halt by other hands.”

The former late-night star also joked about the uncertain future facing the format itself.

“What will become of the Jimmys?” Letterman quipped, referring to Jimmy Kimmel and Jimmy Fallon.

“We’ve got a plan to put them in a captive breeding program,” Colbert shot back.

The drama over Colbert’s cancellation has unfolded as Paramount Skydance moves to finalize its acquisition of Warner Bros. Discovery.

Former Paramount chair Shari Redstone defended the cancellation, insisting late-night television had become “financially not viable.”

“I love Stephen. He does a great job, but we really needed to be in a financially valuable business,” Redstone said last year at Axios’ Media Trends event in New York.

Redstone also rejected suggestions that Colbert’s cancellation was politically motivated, saying the decision had been made “months prior to the announcement.”

The Post has sought comment from Paramount Skydance.

Colbert’s final episode is scheduled to air Thursday, May 21.