One drop rhythm is a reggae style drum beat.

Popularized by Carlton Barrett, long-time drummer of Bob Marley and the Wailers, the creator is disputed, and it has been attributed to drummers including Barrett, and his brother Aston, and Winston Grennan.

The backbeat is characterized by the dominant snare drum stroke (usually a click produced by cross-sticking) and bass drum both sounding on the third beat of every four, while beat one is left empty. Thus, the expected hit on beat one is "dropped," creating the one-drop effect. Dropping out the bass on the "one" of the measure further accentuates the downbeat of the drums creating the rhythm.

This may be seen in the drum notation for the typical rock drum pattern:

and the one drop:

The rockers rhythm is the one drop with a steady bass drum on every eighth note, though one drop is slower than a ska pattern, and rockers is often slower than one drop.

The steppers rhythm is essentially the one drop with a steady bass drum on every quarter note.

An instructive example of this drum beat is Bob Marley and the Wailers' song "One Drop" which talks about this rhythm.