  We present a precise measurement of the lifetime of the 6p 2P_1/2 excited
state of a single trapped ytterbium ion (Yb+). A time-correlated single-photon
counting technique is used, where ultrafast pulses excite the ion and the
emitted photons are coupled into a single-mode optical fiber. By performing the
measurement on a single atom with fast excitation and excellent spatial
filtering, we are able to eliminate common systematics. The lifetime of the 6p
2P_1/2 state is measured to be 8.12 +/- 0.02 ns.
