OASIS is an open-access web portal that enables cancer researchers to perform exploratory and integrative analyses of somatic mutation, copy number changes (CNV) and gene expression data from thousands of tumor, normal tissues and cell lines representing a broad spectrum of malignancies. OASIS provides a powerful resource to the cancer research community by combining one of the largest repositories of multi-omics datasets on the web with intuitive analytics (Fernandez-Banet et al., Nature Meth 13:10, 2016) Registration not required.