A fire at the River House — a posh Midtown East building whose residents include Hollywood starlets, business tycoons and even a former secretary of state — killed an elderly lawyer and his wife Saturday morning.

The blaze broke out around 5:20 a.m. in a ninth-floor apartment of the River House, a 27-story co-op on East 52nd Street near the FDR Drive, where John Merow, 89, and Alice Merow, 85, lived, police said.

Mary Alice, discovered inside with severe burns, was pronounced dead on scene. John was rushed to NewYork-Presbyterian/Weill Cornell Medical Center, where he was also pronounced dead.

Three firefighters were taken to NYU Langone Medical Center — two with serious but non-life-threatening injuries, and one with minor injuries, the FDNY said.

Two other firefighters refused medical attention.

The fire was believed to be an accident caused by a cigarette on the bed, police sources said.

“It was just a very heavy volume of fire on arrival and as the fire marshals work through that they will figure out some of the details of how that happened,” said FDNY Deputy Chief James Coyne.

Built in 1931, The Art Deco-style River House overlooks the East River and is home to the exclusive River Club. Current sale prices for units there range from $3 million to $14 million, according to StreetEasy.

Former secretary of state Henry Kissinger lives in the building.

“It was a sad tragedy for our respected and friendly neighbors,” Kissinger spokewoman Jessica LePorin told the Post. “We are deeply grateful for the firefighters’ rapid action, professionalism, and dedication in controlling the fire.”

Actress Uma Thurman, also a resident, declined to comment to the Post outside the building Saturday.