Pile foundations are usually used when heavy superstructural loads have to be transmitted through weaker subsoil. Piles are also subjected to significant amounts of lateral loads and overturning moments besides axial loads. Lateral loads are in the order of 10-15% of the vertical loads in the case of onshore structures, whereas in the case of coastal and offshore structures, these lateral loads can exceed 30% of the vertical loads. Therefore, proper attention has to be given in designing such pile structures under lateral loads. In recent years, many investigations have addressed the externally bonded fiber-reinforced polymer composites for strengthening of concrete structures. This paper presents an experimental study on glass and carbon fiber-reinforced polymers (GFRP and CFRP) strengthened reinforced concrete (RC) piles subjected to cyclic lateral loads. The effects of GFRP and CFRP strengthening on RC piles were studied. The load deflection, stiffness degradation, and energy dissipation of piles are also presented. (C) 2017 American Society of Civil Engineers.