Molecular genetic techniques have found broad utility in modern marine ecology, and applications continue to grow. Databases of DNA sequences now permit nonexperts to identify eggs and larval stages of many marine animals that were previously mysteries. Molecular identifications of field-collected organisms and tissues are used to help assess population connectivity, investigate marine food webs, and identify marketed commodities. Advances in technology already include prototype development of in situ robotic instrumentation for sampling and molecular identification of animal larvae. Studies of population connectivity, once limited to a few gene loci, are slowly giving way to new genomic arrays of markers and high-throughput methodologies for scoring genotypes. Population genetic theory is providing new computational techniques to assess patterns of population structure, estimate effective population sizes, and infer aspects of demographic history. In this article I review a subset of recent work in this growing area of molecular marine ecology.