Magnetotransport measurements are carried out on nanowires of the Dirac semimetal . Weak antilocalization is observed at 1.9 K, consistent with the presence of strong spin–orbit interaction. With decreasing temperature, Shubnikov–de Haas oscillations are seen, revealing an ultrahigh mobility of 57 000 cm2 Vs at 1.9 K. The strong oscillations display a linear dependence of the Landau‐level index on the inverse of the magnetic field, yielding an intercept that is consistent with a π Berry phase—the signature feature of Dirac fermions. By studying the fundamental properties of Dirac materials, new avenues can be explored by exploiting their unique properties for spintronics and magnetoelectronic devices.