Food frequency questionnaire (FFQ) is a dietary assessment tool delivered as a questionnaire to estimate frequency and, in some cases, portion size information about food and beverage consumption over a specified period of time, typically the past month, three months, or year. FFQs are a common dietary assessment tool used in large epidemiologic studies of nutrition and health. Examples of usage include assessment of intake of vitamins and other nutrients, assessment of the intake of toxins, and estimating the prevalence of dietary patterns such as vegetarianism.

A FFQ includes questions on a set of food and beverage items. For each food or beverage item, there may be questions asking about the following:

In addition to foods and beverages, FFQs often ask about the frequency of intake and dosages of commonly consumed dietary supplements.

A FFQ that aims to capture total dietary intake includes questions on 80 to 120 food and beverage items, and takes 30 to 60 minutes to complete.

FFQs may be interviewer-administered in case of low literacy as well as when being conducted on children.

FFQs are intended for individual rather than household use (i.e., they need to be answered for each individual food consumer). For very young children, the FFQ may be answered by a parent or guardian instead.^{[citation needed]}

FFQs are classified as:

FFQ is a common method for dietary assessment, i.e., for constructing the respondent's diet history. Some other methods include: