Yes, a photon is considered an elementary particle. It is one of the fundamental particles in the Standard Model of particle physics.
Photons are the carriers of the electromagnetic force, which means they are responsible for electromagnetic interactions. They are massless and travel at the speed of light in a vacuum, which is approximately 299,792 kilometers per second (or about 186,282 miles per second).
Elementary particles are defined as particles that are not made up of smaller constituents. In this regard, photons fit the criteria because they do not have any substructure; they cannot be divided into smaller particles. Unlike protons and neutrons, which are composed of quarks, photons are purely energy and have properties such as wavelength and frequency, but no mass or charge.
In summary, photons are fundamental to our understanding of both quantum mechanics and electromagnetic theory, solidifying their status as elementary particles in the universe.