This　paper　presents　a　nonlinear　analysis　method　for　laterally　loaded　large-diameter　monopiles.　The　method　accounts　for　the　effects　of　pile　diameter　and　soil　deformation　on　the　modulus　of　horizontal　subgrade　reaction　by　considering　a　modified　modulus　of　horizontal　subgrade　reaction.　The　solution　considers　the　force　and　moment　equilibrium　of　soil-pile　system　to　calculate　the　response　of　the　monopile　to　lateral　loads.　The　influence　of　the　soil　side　friction　reaction　on　the　ultimate　horizontal　resistance　is　evaluated　considering　the　degradation　of　modulus　of　horizontal　subgrade　reaction　due　to　large　pile　displacement.　The　predictions　of　the　developed　method　compared　favorably　with　the　results　obtained　from　full-scale　field　tests,　centrifuge　model　tests　and　laboratory　model　tests　as　well　as　existing　analytical　methods.　The　developed　analytical　method　is　then　applied　to　study　the　rigid　rotation　behaviour　of　offshore　monopiles.　The　results　demonstrated　that　under　lateral　loading　at　the　pile　head,　the　depth　for　rigid　rotation　point　lies　within　0.62L0.73L　(L　is　pile　length),　and　the　depth　of　the　rotation　point　increases　as　the　pile　diameter　increases.　It　was　also　found　that　the　load　eccentricity　has　a　significant　effect　on　the　depth　of　the　rotation　point.　©　2020　Elsevier　Ltd