MOSIS (Metal Oxide Semiconductor Implementation Service) is multi-project wafer service that provides metal–oxide–semiconductor (MOS) chip design tools and related services that enable universities, government agencies, research institutes and businesses to prototype chips efficiently and cost-effectively.

Operated by the University of Southern California's Information Sciences Institute (ISI), MOSIS combines customers' orders onto shared multi-project wafers that speed production and reduce costs compared with underutilized single-project wafers. Customers are able to debug and adjust designs, or to commission small-volume runs, without making major production investments. Fabrication costs are also shared by combining multiple designs from a single customer onto one "mask set," or wafer template. According to MOSIS, the service has delivered more than 60,000 integrated circuit designs.^[1]

MOSIS was created in 1981 by ISI's Danny Cohen, an Internet pioneer who also developed Voice over Internet Protocol and Video over Internet Protocol.^[2] It was based on the revolutionary VLSI design methodology of Carver Mead and Lynn Conway, who pioneered and/or popularized the use of technology-independent design rules and modular cell-based, hierarchical system design, testing this new approach to rapid prototyping and short-run fabrication at Xerox PARC.^[3] One of the first e-commerce providers, MOSIS also launched the "fabless foundry" industry, in which vendors outsource chip fabrication rather than manufacturing them in-house.^[4] Thousands of students also have learned chip design in MOSIS-associate programs.^[5]

Many early MOSIS users were students trying IC layout techniques from the seminal book Introduction to VLSI Design (ISBN 0-201-04358-0) published in 1980 by Caltech professor Carver Mead^[6] and MIT professor Lynn Conway.^[7][8] Some early reduced instruction set computing (RISC) processors such as MIPS (1984) and SPARC (1987) were run through MOSIS during their early design and testing phases.