  In this paper we develop the theory of non-commutative $\PP^1$-bundles over
commutative (smooth) schemes. Such non-commutative $\PP^1$-bundles occur in the
theory of $D$-modules but our definition is more general. We can show that
every non-commutative deformation of a Hirzebruch surface is given by a
non-commutative $\PP^1$-bundle over $\PP^1$ in our sense.
