Abstract: A trailer hitch spring pin lock mechanism is provided. The mechanism includes a hitch receiver secured to a trailer hitch main body. The trailer hitch main body may be secured to a chassis of a vehicle. The hitch receiver includes a side wall forming a hitch receiver slot within and a front opening leading into the hitch receiver slot. A side opening is formed through the side wall. The present invention further includes an outer plate having an outer plate opening formed there through. The present invention further includes a main pin. A protrusion 40 extends laterally from the main pin. The main pin runs through the outer plate opening and the side opening. A spring is secured around the main pin in between the protrusion and the outer plate, biasing the main pin within the hitch receiver slot.