The present invention provides a novel crystalline form of remdesivir, remdesivir Form APO-I, including remdesivir and dimethyl sulfoxide, compositions and processes for the preparation thereof, the use of this crystalline form in the treatment of a viral infection, and methods of treating viral infections using the same, and in particular, a viral infection caused by Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2).