Ranjan Mathai Wednesday retired as foreign secretary and handed over charge to his successor Sujatha Singh.
Singh, 59, was earlier ambassador to Germany.
The 1976 batch Indian Foreign Service officer will have a fixed tenure of two years.
Mathai assumed charge on Aug 1, 2011 with a two-year term.
Singh served as ambassador to Germany (2012-2013) and high commissioner to Australia (2007-2012).