Geoffrey Nigel Gilbert (born 21 March 1950) is a British sociologist and a pioneer in the use of agent-based models in the social sciences. He is the founder and director of the Centre for Research in Social Simulation (University of Surrey), author of several books on computational social science, social simulation and social research and past editor of the Journal of Artificial Societies and Social Simulation (JASSS), the leading journal in the field.

A Cambridge engineering graduate (Emmanuel College), he turned to the sociology of scientific knowledge for his PhD under the direction of Michael Mulkay. He was a lecturer at the University of York (1974–76) and then joined the University of Surrey where he became a professor in the Department of Sociology in 1991. At the University of Surrey he founded the Social and Computer Sciences research group in 1984 with a grant from the Alvey Programme. The group focused on applying social science to the design of intelligent knowledge-based systems. Later he established the Centre for Research in Social Simulation (1997), and the Digital World Research Centre (1998). He served as a Pro-Vice-Chancellor of the University of Surrey (1998–2005) and he is the current Director of its Institute of Advanced Studies. He served as a member of the Council of the Economic and Social Research Council. from 2017 to 2020.

Gilbert and Mulkay (1984) is a key contribution on the use of discourse analysis methods in the sociology of scientific knowledge. By applying discourse analysis to extensive qualitative data on a scientific dispute in the field of chemistry, Gilbert and Mulkay account for the social processes that underpin knowledge production, especially when consensus has not yet been established within the scientific community.

With Sara Arber, he was a pioneer in the use for academic analysis of computer files of survey data collected by the Office of Population Censuses and Surveys, a data source that has now become commonplace in sociology.

The regulations determining what claimants of UK welfare benefits are entitled to (e.g. income support, tax credits, Disability Living Allowance) are complicated and often very difficult for claimants to apprehend unaided. With the growing availability of personal computers in the 1980s, he realised that an interactive program, designed for claimants themselves to use, could be helpful. He developed a prototype, which was taken up by both the then Department of Health and Social Security and Citizens Advice Bureaux, and which was the forerunner of the systems nowadays routinely used in advice centres. This work also contributed to understanding the interface requirements for publicly accessible computer systems, using graphical interfaces and, later, speech dialogue interfaces .

Nigel Gilbert is one of the founders of modern computational sociology, a discipline that merges social science research with simulation techniques with the goal of modelling complex policy issues and fundamental aspects of human societies. His first work in this area was a project on modelling the emergence of organised society in prehistoric France, with Jim Doran . While this was only moderately successful, it led him to organise in 1992 the first of an influential series of workshops on 'Simulating Societies’ Later he established:

In 1997, CRESS received funding from the FAIR programme of the European Commission for a project called IMAGES: Improving agri-environmental policies–a simulation approach to the role of the cognitive properties of farmers and institutions (1997–2000). This was the first of many Commission funded projects using social simulation to which he contributed, such as SEIN, FIRMA, SIMWEB, EMIL, NEMO, NEWTIES, PATRES, QLectives, ePolicy, TellMe, GLODERS and P2Pvalue .

In 1999, Nigel Gilbert and Klaus G. Troitzsch published Simulation for the social scientist, the first "how to" text book on social simulation and, in 2008, Agent-based Models, now one of the standard references on agent-based modelling.