Daniel R. Day (born August 8, 1944), known as Dapper Dan, is an American fashion designer and haberdasher from Harlem, New York. His store, Dapper Dan's Boutique, operated from 1982 to 1992 and is most associated with introducing high fashion to hip hop culture; its clientele includes Mike Tyson, Eric B. & Rakim, Salt-N-Pepa, LL Cool J, and Jay-Z. In 2017, he launched a fashion line with Gucci, with whom he opened a second store and atelier, Dapper Dan's of Harlem, in 2018. Dan is included in Time's 100 Most Influential People of 2020.

Dan was born in Harlem, New York, in 1944, at home with his grandmother acting as a midwife. He grew up on 129th and Lexington Avenue with three brothers and three sisters. His father, Robert, was a civil servant and his mother, Lily, a homemaker. All nine of them lived in a three-bedroom apartment. He recalls horses and buggies still on the streets in his early childhood, in the post-World War II days of Manhattan. By age 13, he was a skilled gambler; his success as a gambler helped him finance his first store.

Dapper Dan became tired of the street life after listening to a Malcolm X speech. Malcolm X said, "If you want to understand the flower, study the seed." This prompted Dan to indulge in studying at the Countee Cullen Library. He soon went back to school and entered into an academic program sponsored by the Urban League and Columbia University. In the 1960s, Dan worked for a Harlem newspaper called Forty Acres and a Mule, as he initially wanted to become a writer. During this time he went through a life-style change and became a vegetarian. In 1968–74, he toured Africa as part of the Columbia University and the Urban League academic program. When Dan returned to New York in 1974, he decided to be a clothier, and first sold shoplifted items out of his car. Dapper Dan's Boutique, located on 125th Street between Madison and Fifth Avenues, opened in 1982, and at times was open 24 hours a day, seven days a week. Dan approached his designs through personal experience, specifically from his previous jobs. Being a professional gambler taught him that what a person wears will influence how people interact with them, so he used this unspoken language in his designs. Dan's previous disciplines are also what prepared him to simultaneously be a creative director and businessman. Additionally, he was an observer and approached his designs from a psychological point of view. When working with a new client, he would ask himself "Who are they?" and "What do they want?"