A positive electrode active material according to the present disclosure includes: a lithium composite oxide which includes Mn and at least one selected from the group consisting of F, Cl, and N, and S. The lithium composite oxide has a crystalline structure which belongs to the space group Fd-3m, and a relationship 1.40≤intensity ratio IMn1/IMn2≤1.90 is satisfied. The intensity ratio IMn1/IMn2 is a ratio of an intensity IMn1 to an intensity IMn2. The intensity IMn1 and the intensity IMn2 are intensities of a first proximity peak and a second proximity peak, respectively, of the Mn in a radial distribution function of the Mn included in the lithium composite oxide.