P-branes or branes are terms from quantum superstring theory used to refer to membrane-like structures of one to eleven dimensions that arise in equations of this heavily mathematical theory.

They were originally based on the implications of one-dimensional strings. By the mid-1990s it became apparent that string theories could be extended to also include non-1-dimensional objects called p-branes. The name "p-brane" comes from a generalization of the two-dimensional "membrane" to p-dimensional p-branes. Strings can be referred to as 1-branes. P-brane theories can contain various fundamental components such as point-like objects (0-branes), two dimensional membranes (2-branes), three-dimensional objects (3-branes), and objects of other dimensions up to eight or nine. M-theory seems to contain membranes and 5-branes.

See also: Brane, D-branes

"p-brane" is also the name of an EP by the band Plaid