The present invention relates to crystalline forms of cabotegravir sodium and to methods for their preparation. Furthermore, the invention relates to a pharmaceutical composition comprising one of said crystalline forms of cabotegravir sodium, preferably in a predetermined and/or effective amount, and at least one pharmaceutically acceptable excipient. The pharmaceutical composition of the present invention can be used as a medicament, in particular for the treatment and/or prophylaxis of viral infections such as HIV infections.