  We find the orbit of the Neptune-sized exoplanet HAT-P-11b to be highly
inclined relative to the equatorial plane of its host star. This conclusion is
based on spectroscopic observations of two transits, which allowed the
Rossiter-McLaughlin effect to be detected with an amplitude of 1.5 m/s. The
sky-projected obliquity is 103_{-10}^{+26} degrees. This is the smallest
exoplanet for which spin-orbit alignment has been measured. The result favors a
migration scenario involving few-body interactions followed by tidal
dissipation. This finding also conforms with the pattern that the systems with
the weakest tidal interactions have the widest spread in obliquities. We
predict that the high obliquity of HAT-P-11 will be manifest in transit light
curves from the Kepler spacecraft: starspot-crossing anomalies will recur at
most once per stellar rotation period, rather than once per orbital period as
they would for a well-aligned system.
