Provided is a positive electrode active material, a positive electrode, or a secondary battery having high charge load characteristics. The positive electrode active material includes a lithium complex oxide having a layered rock-salt structure. The lithium complex oxide contains lithium, a metal element including at least one of cobalt and nickel, and potassium. A ratio of a substance amount of potassium contained in the lithium complex oxide to a substance amount of the metal element included in the lithium complex oxide is 0.0005 or more and 0.03 or less. In the lithium complex oxide, potassium is distributed so as to extend in a direction intersecting a <001> direction of the layered rock-salt structure.