We show that the requirement of Poincaré invariance (more specifically invariance under boosts/rotations that mix brane directions with transverse directions) places severe constraints on the form of actions describing multiple D-branes, determining an infinite series of correction terms to the currently known actions. For the case of D0-branes, we argue that up to field redefinitions, there is a unique Lorentz transformation rule for the coordinate matrices consistent with the Poincaré algebra. We characterize all independent Poincaré invariant structures by describing the leading term of each and providing an implicit construction of a Lorentz invariant completion. Our construction employs new matrix-valued Lorentz covariant objects built from the coordinate matrices, which transform simply under the (extremely complicated) Lorentz transformation rule for the matrix coordinates.1 These could be the usual D0-branes of type IIA string theory with d = 9, or any other pointlike D-branes arising from higher dimensional branes wrapped on cycles in a compactification.2 Here, all bulk fields have been set to zero.3 Indeed, to our knowledge none of the actions for multiple D-branes that have appeared previously in the literature are Poincaré invariant apart from the cases p = −1 and p = 9 which are trivial.4 Early work on understanding the structure of non-abelian D-brane actions based on general principles was initiated by Douglas [2,3]. For general reviews discussing the physics of multiple D-branes, including many additional references, see [4,5].