LSI Architects LLP is a London and Norwich-based firm of around 45 architects, technologists, designers, computer specialists and support staff, working primarily in Norfolk and the Eastern Region, but also in Scotland, the Midlands, the North-West and the Home Counties.

The practice is one of Norwich's oldest Architectural Practices. LSI can trace its history in the locality for well over a century, and most recently in the form of Lambert, Scott & Innes.

Following the retirement of the founding partners, the practice name changed in 2002 to LSI Architects, and during the same year the practice became a Limited Liability Partnership (LLP).