Biographies are generally secondary sources as they present information about the life of someone else. The author will likely consult primary sources to compose the biography, such as personal letters, archival records (e.g., birth registries), or diaries. In contrast, an autobiography is a primary source as it is a firsthand account of one’s own life.
However, if you are researching the ways in which a particular figure’s life has been represented, then biographies written about the person would function as primary sources.
Any time a biography or other source is used, it must be accompanied by a citation and reference entry to avoid plagiarism. You can use QuillBot’s Citation Generator to automatically generate citations for all types of sources.