FABP9 (Fatty acid binding protein 9), also known as PERF15 or T-FABP, is a member of fatty acidbinding proteins (FABPs) which are a family of small, highly conserved, cytoplasmic proteins to bind long-chain fatty acids and other hydrophobic ligands. It is found in midpachytene spermatocytes and round spermatids, and constitutes part of the perinuclear theca.