The Classen (Originally Citizens Bank Tower) is a residential high-rise in the uptown section of Oklahoma City, near the city's Paseo Arts District and Asian District. The tower has 21 floors and is 287 feet tall. It is currently the third tallest residential building in the city. In 2010, the property was listed on the National Register of Historic Places.

The building was completed in 1967 as the headquarters of the defunct Citizens National Bank. The tower was then converted to a residential apartment building and serves as one of the premiere places to live in the city. The property is a significant building in Oklahoma City with its hexagonal plan, slender profile, unusual sunscreens and rigorously sculpted crown. It was among the first tall office buildings to be erected outside of downtown Oklahoma City, setting the standard for other distinctive large freestanding suburban skyscrapers. The Citizens Bank Tower was designed by Robert Roloff of the firm Bozalis, who considered it a tribute to Frank Lloyd Wright and his Price Tower constructed in Bartlesville, Oklahoma. The interior of the tower has been adapted to apartment units for contemporary use. Citizens Bank Tower has been listed on the National Register of Historic Places since March 8, 2010. It was announced as the featured listing in the National Park Service's weekly list of March 19, 2010.