Japan holds the record for the smallest rocket to reach orbit with the SS-520, which put a cubesat into orbit in 2018.

Its dimensions according to Wikipedia:

Height – 31 feet (9.54 meters)

Weight – 2.9 tons (2.6 metric tons)

Diameter – 20 inches (52 centimeters)

Payload to Low-Earth Orbit – ~9 lbs (4 kg)