A planetary gear train of an automatic transmission may include: an input shaft; an output gear; a first planetary gear set including first sun gear, first planet carrier, and first ring gear; a second planetary gear set including second sun gear, second planet carrier, and second ring gear; a third planetary gear set including third sun gear, third planet carrier, and third ring gear; a fourth planetary gear set including fourth sun gear, fourth planet carrier, and fourth ring gear; a first rotation shaft including the first sun gear; a second rotation shaft including the first planet carrier, the second ring gear, the third planet carrier, and the fourth ring gear; a third rotation shaft including the first and third ring gears; a fourth rotation shaft including the second sun gear and selectively connected to a transmission housing; a fifth rotation shaft including the second planet carrier, selectively connected to the first rotation shaft and to the third rotation shaft, and directly connected to the input shaft; a sixth rotation shaft including the third sun gear; a seventh rotation shaft including the fourth sun gear, selectively connected to the sixth rotation shaft, and to the transmission housing; and an eighth rotation shaft including the fourth planet carrier, selectively connected to the sixth rotation shaft, and directly connected to the output gear.