Opisthorchiasis is a neglected, tropical disease caused by the carcinogenic Asian liver fluke, Opisthorchis viverrini. This hepatobiliary disease is linked to malignant cancer (cholangiocarcinoma, CCA) and affects millions of people in Asia. No vaccine is available, and only one drug (praziquantel) is used against the parasite. Little is known about O. viverrini biology and the diseases that it causes. Here we characterize the draft genome (634.5 Mb) and transcriptomes of O. viverrini, elucidate how this fluke survives in the hostile environment within the bile duct and show that metabolic pathways in the parasite are highly adapted to a lipid-rich diet from bile and/or cholangiocytes. We also provide additional evidence that O. viverrini and other flukes secrete proteins that directly modulate host cell proliferation. Our molecular resources now underpin profound explorations of opisthorchiasis/CCA and the design of new interventions.