A quantity surveyor (QS) is a construction industry professional with expert knowledge on construction costs and contracts. Qualified professional quantity surveyors are known as Chartered Surveyors (Members and Fellows of RICS) in the UK and Certified Quantity Surveyors (a designation of AIQS) in Australia and other countries. In some countries such as Canada, South Africa, Kenya and Mauritius, qualified quantity surveyors are known as Professional Quantity Surveyors, a title protected by law.

Quantity surveyors are responsible for managing all aspects of the contractual and financial side of construction projects. They help to ensure that the construction project is completed within its projected budget. Quantity surveyors are also hired by contractors to help with the valuation of construction work for the contractor, help with bidding and project budgeting, and the submission of bills to the client.