Yrjo Kukkapuro, a Finnish furniture designer who devoted his restless creative energies to sedentary comfort, creating dozens of chairs that coddled sitters and lent a zesty flair to their surroundings, died on Feb. 8 at his home in Kauniainen, Finland. He was 91.

His death was confirmed by his daughter, Isa Kukkapuro-Enbom.

In his seven-decade career, Mr. Kukkapuro designed a variety of furnishings for homes, offices and public institutions. But he was best known for his seating.

“Almost every Finn has sat on a chair he designed — at a metro station, in a bank, at a school or in a library,” his company, Studio Kukkapuro, said in a news release.

An experimental modernist who was invigorated by the availability of lightweight synthetic materials after World War II, Mr. Kukkapuro made abundant use of fiberglass and other plastics, which could be sculpted to the human form. He also favored organic materials like steam-bent plywood and leather.

Referring to Mr. Kukkapuro’s relentless pursuit of ergonomics, Jukka Savolainen, a former director of the Design Museum in Helsinki who now heads the Alvar Aalto Museum in Finland, described him as “playful with form and color, but always thinking about the user at the center.”

Among Mr. Kukkapuro’s most celebrated designs was Karuselli, a slick fiberglass lounge chair with exuberant leather upholstery rolling over the edges. He attached the bulbous bucket seat to the flowerlike base with a steel bracket that permitted the chair — whose name means “carousel” in Finnish — to both swivel and rock.