  We present the first experimental evidence, supported by theory and
simulation, of spatiotemporal optical vortices (STOVs). Quantized STOVs are a
fundamental element of the nonlinear collapse and subsequent propagation of
short optical pulses in material media. A STOV consists of a ring-shaped null
in the electromagnetic field about which the phase is spiral, forming a dynamic
torus which is concentric with and tracks the propagating pulse. Depending on
the sign of the material dispersion, the local electromagnetic energy flow is
saddle or spiral about the STOV. STOVs are born and evolve conserving
topological charge; they can be simultaneously created in pairs with opposite
windings, or generated from a point null. Our results, here obtained for
optical pulse collapse and filamentation in air, are generalizable to broad
class of nonlinearly propagating waves.
