Star Trek: Department of Temporal Investigations is a series of Star Trek novels and eBook novellas published by Pocket Books. The series began in 2011, with Watching the Clock. Forgotten History was released in 2012, followed by The Collectors in 2014, and Time Lock in 2016. All four stories were written by Christopher L. Bennett.

The series focuses on the Federation Department of Temporal Investigations, in particular, Agents Marion Dulmur and Gariff Lucsly who were first introduced in the Star Trek: Deep Space Nine episode Trials and Tribble-ations. The novels frequently reference, and expand upon, temporal events seen throughout the televised episodes of all six television series, with Watching The Clock featuring characters from Star Trek: Enterprise, The Next Generation, and Titan novels. Likewise Forgotten History features those from The Original Series and The Animated Series.