The objectives of this research are to determine: 1) the effect of William Flexion exercises towards complaints of lower back pain, 2) the effect of core stability exercises towards the complaints of lower back pain, 3) the difference in the effect between William Flexion and core stability exercises towards the complaints of low back pain. The type of this research was a two group pretest-posttest design experiment where the William Flexion and core stability exercise methods were treated routinely 3 times a week for 4 weeks. The research was conducted at the Karang Malang Campus, Yogyakarta State University, the research period was 4 weeks from mid-October to mid-November 2023. The research sample was for about 40 people, 20 people were given the treatment of William Flexion exercise group and 20 people were given the Core Stability exercise method. The data analysis technique used hypothesis testing with t test analysis. The results of the study showed that 1) There was an effect of William Flexion training on pain (p < 0.05), range of motion (p < 0.05) and function (p < 0.05) on complaints of lower back pain. 2) There is an effect of Core Stability exercises on pain (p0.05), range of motion (p>0.05) and function (p>0.05) in William Flexion and Core Stability exercises in cases of low back pain. It was concluded from this research that William Flexion and Core Stability exercises can reduce complaints of lower back pain. There is no significant difference between William Flexion and Core Stability exercises. The exercise application can be adjusted to suit your needs.