We have developed a novel anisotropic wet chemical etching process for V-grooves on (001) InP substrates. The etching was carried out in three steps with solutions of 0.1 volume percent bromine in methanol and H2SO4:H2O:H2O2 (3:1:1). The etching mask was a 30 nm thick Si3N4 film patterned with conventional photolithography and plasma enhanced chemical vapor deposition. It exhibited excellent properties with respect to undercutting. The resulting V-grooves had very smooth {111} A sidewalls and a tip radius below 10 nm. The uniformity of the etched profile was excellent both along the groove axis and from groove to groove.