List of Billboard Easy Listening number ones of 1966

In 1966, Billboard magazine published a chart ranking the top-performing songs in the United States in the easy listening market. The chart, which in 1966 was entitled Easy Listening, has undergone various name changes and since 1996 has been published under the title Adult Contemporary. In 1966, 18 songs topped the chart based on playlists submitted by easy listening radio stations and sales reports submitted by stores.

In the year's first issue of Billboard, Roger Miller moved up one place to number one with "England Swings", however the song held the top spot for only a single week before being replaced by Al Martino's "Spanish Eyes", which spent four weeks atop the chart. Immediately after Martino's run at number one, Frank Sinatra, one of the most popular and influential musical artists of the 20th century, gained his first Easy Listening chart-topper with "It Was a Very Good Year". Sinatra, who was experiencing a career resurgence at the age of 50, achieved several chart distinctions in 1966. He had the most number ones of the year, topping the chart with four singles, spent the most total weeks in the top spot with 13, and had the longest unbroken run at number one when "Strangers in the Night" spent seven consecutive weeks topping the listing. Although Sinatra reportedly did not care for "Strangers in the Night", it also topped Billboard's pop music chart, the Hot 100, received the award for best original song at the 24th Golden Globe Awards, and claimed four Grammy Awards at the 1967 ceremony.

Two other Easy Listening number ones also topped the Hot 100. In the early part of the year, Staff Sergeant Barry Sadler, a serving soldier in the United States military, reached the top of both listings with "The Ballad of the Green Berets". The patriotic song went on to be the biggest-selling single of the year in the U.S. In December, the British novelty act the New Vaudeville Band reached number one on both charts with the 1920s-styled "Winchester Cathedral", the only song of the group's career to achieve major chart success in the United States. Neither act topped the Easy Listening chart again in their career; the Ray Conniff Singers, Margaret Whiting, and Roger Williams also achieved their only number ones on the listing during 1966.