Mathematics Department held a Guest Lecture Webinar on Tuesday, May 24, 2022, with the theme “Introducing Fractional Calculus”. The Guest Lecture Webinar is held online through the Zoom Meeting Conference application. This Guest Lecture Webinar activity is open to the public, whether students from UNU Blitar or from other universities. Mr. Minanur Rohman, M.Sc delivered the Guest Lecture Webinar material. He is one of the Lecturers at Ondokuz Mayıs University, Turkey. In the webinar, he explained the introduction, objectives, some book references, and how to solve some calculus problems. Calculus is a science used to gain a deep and detailed understanding of space, motion, and time. He systematically explained the discussion of calculus material and answered several student questions in detail so that they could be understood by students who participated in this webinar activity. This Guest Lecture Webinar activity is a means for students to get to know thoroughly about calculus which is a branch of mathematical analysis that is often studied in the lecture process. By holding this Guest Lecture Webinar, it is hoped that students can get to know more about calculus material, and make students more enthusiastic about carrying out lectures.