In this memoir, Yang-Mills field curvature and current are described as elements of cohomology groups on ambitwistor space, and it is shown that the Yang-Mills current corresponds to the third-order obstruction to extending the corresponding vector bundle. There is also a description of the Yang-Mills field's action density. In addition, several groups of solutions to various differential equations on Miskowski space are characterized as elements of various cohomology classes over ambitwistor space.