6223 Dahl, provisional designation 1980 RD1, is a carbonaceous asteroid from the middle region of the asteroid belt, approximately 18 kilometers in diameter. It was discovered on 3 September 1980, by Czech astronomer Antonín Mrkos at Kleť Observatory near České Budějovice in the Czech Republic.
The dark C-type asteroid orbits the Sun at a distance of 2.4–3.1 AU once every 4 years and 6 months (1,653 days). Its orbit has an eccentricity of 0.12 and an inclination of 4° with respect to the ecliptic. The first precovery was taken at the U.S. Goethe Link Observatory in 1949, extending the asteroid's observation arc by 31 years prior to its discovery.
In November 2011, a rotational light-curve for this asteroid was obtained by Brett Waller at the U.S. Cedar Green Observatory in Virginia. It gave a rotation period of 7000333000000000000♠3.33±0.01 hours with a brightness variation of 0.43 in magnitude (U=2).
According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, the asteroid measures 19.6 kilometers in diameter and its surface has an low albedo of 0.034, while the Collaborative Asteroid Lightcurve Link assumes a standard albedo for carbonaceous asteroids of 0.057 and calculates a diameter of 16.8 kilometers, as the higher the albedo (reflectivity), the lower the body's diameter at a constant absolute magnitude.
The minor planet was named in memory of the Welsh author Roald Dahl (1916–1990), known for his classic children's books Willy Wonka and the Chocolate Factory and James and the Giant Peach. Naming citation was published on 28 August 1996 (M.P.C. 27735).