Manifestly Lorentz Invariant Chiral Boson Action

A manifestly Lorentz invariant action is found for the Floreanini-Jackiw chiral boson. The method involves a novel chiral reduction of the phase-space action for a string and can be adapted to describe chiral bosons on the heterotic string worldsheet. A similar manifestly Lorentz invariant action is found for an entire class of conformal chiral 2 k -form electrodynamics in (4 k +2 ) dimensions which includes the Floreanini-Jackiw theory as the k =0 case.