The nature and origin of magnetic fields in early-type stars

I review our current knowledge of magnetic fields in stars more massive than around 1.5 Msun, in particular their nature and origin. This includes the strong magnetic fields found in a subset of the population and the fossil field theory invoked to explain them; the subgauss fields detected in Vega and Sirius and their possible origin; and what we can infer about magnetic activity in massive stars and how it might be linked to subsurface convection.