Updated publication reference for PubMed record(s): 27561551. A cell line representative of human high-grade serous ovarian cancer (HGSOC) should not only resemble its tumor of origin at the molecular level, but also demonstrate functional utility in pre-clinical investigations. Here we report the integrated proteomic analysis of 26 ovarian cancer cell lines, HGSOC tumors, immortalized ovarian surface epithelial cells, and fallopian tube epithelial cells via a single-run mass spectrometric workflow. The in-depth quantitation of > 10,000 proteins results in three distinct cell line categories: epithelial (group I), clear cell (group II), and mesenchymal (group III). We identify a 67-protein cell line signature, which separates our entire proteomic dataset, as well as a confirmatory publicly available CPTAC/TCGA tumor proteome dataset, into a predominantly epithelial and mesenchymal HGSOC tumor cluster. This proteomics-based epithelial/mesenchymal stratification of cell lines and human tumors indicates a possible origin of HGSOC either from the fallopian tube or from the ovarian surface epithelium.