A lab-on-a-chip (LOC) is a device that integrates one or several laboratory functions on a single chip of only millimeters to a few square centimeters to achieve automation and high-throughput screening. LOCs deal with the handling of extremely small fluid volumes down to less than pico liters. Lab-on-a-chip devices are a subset of Micro-electro-mechanical systems (MEMS) devices and often indicated by "Micro Total Analysis Systems" (µTAS) as well. LOC is closely related to, and overlaps with, microfluidics which describes primarily the physics, the manipulation and study of minute amounts of fluids. However, strictly regarded "Lab-on-a-Chip" indicates generally the scaling of single or multiple lab processes down to chip-format, whereas "µTAS" is dedicated to the integration of the total sequence of lab processes to perform chemical analysis. The term "Lab-on-a-Chip" was introduced later on when it turned out that µTAS technologies were more widely applicable than only for analysis purposes.

Lab on a Chip is a peer-reviewed scientific journal which publishes original (primary) research and review articles on any aspect of miniaturisation at the micro and nano scale. Lab on a Chip is published monthly by the Royal Society of Chemistry (RSC) and the editor-in-chief is Harp Minhas. The journal was established in 2001 and hosts other RSC publications: Highlights in Chemical Technology and Highlights in Chemical Biology. According to the Journal Citation Reports, the journal has a 2014 impact factor of 6.115.