William B. F. Ryan (born 1 September 1939 in Troy, New York, USA) is an American marine geologist and geophysicist known for his pioneering work in deep‑sea research and oceanographic instrumentation. He earned his B.A. from Williams College in 1961 and his Ph.D. in Geophysics from Columbia University in 1969. Over a long career at the Lamont–Doherty Earth Observatory, he held roles including Adjunct Professor of Geology, Doherty Senior Scientist, and (since 2014) Doherty Senior Scholar, mentoring generations of earth scientists and participating in research expeditions worldwide. Among his many scientific contributions is his involvement in early sonar‑based searches for the wreck of the RMS Titanic in the early 1980s. His research spans marine geology, seafloor mapping, plate tectonics, and paleoclimate, and he has received honors including the Society for Sedimentary Geology Shepard Medal and election to the Accademia Nazionale dei Lincei.