The paper introduces TEMPO2, a new pulsar timing package designed to address the limitations of existing packages like TEMPO1. TEMPO2 aims to achieve a precision of 1 ns, significantly improving upon the 100 ns precision of TEMPO1. It is compliant with the general relativistic framework of the IAU 1991 and 2000 resolutions, using the International Celestial Reference System, Barycentric Coordinate Time, and up-to-date precession, nutation, and polar motion models. The package provides a set of tools for analyzing and visualizing pulsar timing data, including features for handling clock corrections, atmospheric propagation delays, Einstein delay, Roemer delay, Shapiro delay, and frequency-dependent parameters. TEMPO2 also includes routines for fitting pulsar parameters, such as spin frequency and derivatives, astrometric parameters, and binary parameters, with detailed descriptions of the fitting algorithms and their accuracy. The paper highlights the improvements over TEMPO1, particularly in handling systematic errors and the ability to analyze multiple pulsars simultaneously.The paper introduces TEMPO2, a new pulsar timing package designed to address the limitations of existing packages like TEMPO1. TEMPO2 aims to achieve a precision of 1 ns, significantly improving upon the 100 ns precision of TEMPO1. It is compliant with the general relativistic framework of the IAU 1991 and 2000 resolutions, using the International Celestial Reference System, Barycentric Coordinate Time, and up-to-date precession, nutation, and polar motion models. The package provides a set of tools for analyzing and visualizing pulsar timing data, including features for handling clock corrections, atmospheric propagation delays, Einstein delay, Roemer delay, Shapiro delay, and frequency-dependent parameters. TEMPO2 also includes routines for fitting pulsar parameters, such as spin frequency and derivatives, astrometric parameters, and binary parameters, with detailed descriptions of the fitting algorithms and their accuracy. The paper highlights the improvements over TEMPO1, particularly in handling systematic errors and the ability to analyze multiple pulsars simultaneously.