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A D8-brane is a D-brane with eight spatial directions and a nine-dimensional worldvolume. In ten-dimensional type IIA superstring theory, it has one transverse spatial direction, so it acts as a domain wall. Its charge is associated with a nine-form Ramond–Ramond potential.

The dual zero-form field strength is the Romans mass; its value can jump across a charged D8-brane. Consequently a D8-brane cannot simply be inserted into the elementary massless M-theory circle duality dictionary used for lower-dimensional IIA branes. Its gravitational matching and scalar-field profiles must be treated consistently on both sides of the wall.^[ref]

Massive type IIA supergravity is a deformation of type IIA supergravity with a nonzero zero-form Ramond–Ramond sector field strength, the Romans mass $F_0=m$. The parameter modifies field strengths, gauge transformations and scalar interactions; it is not a statement that every field, including the graviton, has acquired an ordinary particle mass.

In the presence of a D8-brane, the value of $F_0$ can differ on the two sides of the brane. This links the deformation to charged domain-wall solutions and distinguishes it from the simplest circle reduction of eleven-dimensional supergravity. The limit $m=0$ recovers the ordinary massless theory, but a nonzero flux must be retained consistently in both field equations and source matching.^[ref]