Clarence Samuel Stein (June 19, 1882 – February 7, 1975) was an American urban planner, architect, and writer, a major proponent of the garden city movement in the United States known for the Radburn concept.

Intense and self-absorbed, the young Stein had a nervous collapse shortly before he was scheduled to leave for college, experiencing a bout of what was then called neurasthenia for which he was sent to Florida to endure a rest cure.

He returned to New York and worked in his family's casket business, where the combination of physical and mental labor matched the philosophy in which he had been educated, much in keeping with his contemporary John Dewey.

After a year or so, he prepared to attend college, embarking on an American version of the Grand Tour: travel to the artistic and cultural centers of Europe, in this case in the company of his father.

In concert with his brothers and a small cohort of like-minded young men, many of whom would be influential partners for the rest of his career, Stein started the Young Men's Municipal Club, an organization modeled on many other such burgeoning social amelioration movements (Jane Adams's, Hull House is an example) and dedicated to studying and then agitating for improvements to the chaotic life of the modern city.

While at work on that mission, Stein began to take classes at Columbia University, but they were not the traditional liberal-arts courses common at an Ivy League academy.

Upon returning to America, Stein joined the office of the progressive, eclectic architect Bertram Goodhue and his more eccentric partner Ralph Adams Cram in 1911 and contributed to three of Goodhue's large-scale projects of that time: the Panama–California Exposition in San Diego, California, the company town of Tyrone, New Mexico, and the master plan and individual buildings for the California Institute of Technology in Pasadena.

The two were influential in the 1930s, designing New Town projects, sponsored by New Deal visionaries: Radburn, New Jersey, Sunnyside Gardens, Queens, and Chatham Village, Pittsburgh.

The vision for Radburn was of an integrated self-sustaining community, surrounded by greenbelts, specialized automotive thoroughfares (main linking roads, serviced lanes for direct access to buildings, and express highways), and a complete separation of auto and pedestrian traffic.

This grand vision was informed by the lessons of Sunnyside, and by the comparable city-planning work of Ernst May in Germany (researched by a young Catherine Bauer), but the experiment was never completed because of the economic pressures of the Depression.

Among Stein's other urban-planning credits are the five-city-block Hillside Homes in Williamsbridge, the Bronx, as a Public Works Administration project in 1935; part of the massive wartime labor-force housing at the Walt Whitman Houses in Fort Greene, Brooklyn; Baldwin Hills Village (now the Village Green) in Los Angeles, California in 1941; and his only postwar commission, the re-planning of Kitimat, British Columbia, in 1951.