Implicate order and explicate order are ontological concepts for quantum theory coined by theoretical physicist David Bohm during the early 1980s. They are used to describe two different frameworks for understanding the same phenomenon or aspect of reality. In particular, the concepts were developed in order to explain the bizarre behaviors of subatomic particles which quantum physics describes and predicts with elegant precision but struggles to explain.

In Bohm's Wholeness and the Implicate Order, he used these notions to describe how the appearance of such phenomena might appear differently, or might be characterized by, varying principal factors, depending on contexts such as scales. The implicate (also referred to as the "enfolded") order is seen as a deeper and more fundamental order of reality. In contrast, the explicate or "unfolded" order includes the abstractions that humans normally perceive. As he wrote:

The notion of implicate and explicate orders emphasizes the primacy of structure and process over individual objects. The latter are seen as mere approximations of an underlying process. In this approach, quantum particles and other objects are understood to have only a limited degree of stability and autonomy.

Bohm believed that the weirdness of the behavior of quantum particles is caused by unobserved forces, maintaining that space and time might actually be derived from an even deeper level of objective reality. In the words of F. David Peat, Bohm considered that what we take for reality are "surface phenomena, explicate forms that have temporarily unfolded out of an underlying implicate order." That is, the implicate order is the ground from which reality emerges.

Bohm, his colleague Basil Hiley, and other physicists of Birkbeck College worked toward a model of quantum physics in which the implicate order is represented in the form of an appropriate algebra or other pregeometry. They considered spacetime itself as part of an explicate order that is connected to an implicate order that they called pre-space. The spacetime manifold and the properties of locality and nonlocality all arise from an order in such pre-space. A. M. Frescura and Hiley suggested that an implicate order could be carried by an algebra, with the explicate order being contained in the various representations of this algebra.

In analogy to Alfred North Whitehead's notion of "actual occasion," Bohm considered the notion of moment – a moment being a not entirely localizable event, with events being allowed to overlap  and being connected in an overall implicate order:

I propose that each moment of time is a projection from the total implicate order. The term projection is a particularly happy choice here, not only because its common meaning is suitable for what is needed, but also because its mathematical meaning as a projection operation, P, is just what is required for working out these notions in terms of the quantum theory.

Bohm emphasized the primary role of the implicate order's structure: