This chapter underscores the indispensable role of ultrasonography in advancing assisted reproductive technology (ART), with a structured focus on three core clinical applications: ovarian reserve assessment, ovulation monitoring, and ultrasound-guided interventions. Ovarian reserve evaluation employs ultrasonographic markers such as antral follicle count (AFC), ovarian volume, and Doppler blood flow analysis to quantify follicular function and predict reproductive potential, guiding personalized treatment strategies. In cycle management, serial ultrasonography enables meticulous tracking of follicular development and endometrial changes in both natural and stimulated cycles, ensuring precise timing of ovulation induction and optimization of controlled ovarian hyperstimulation (COH) protocols. During ART procedures, transvaginal ultrasound provides real-time visualization for oocyte retrieval, enhancing procedural accuracy while minimizing invasiveness, whereas transabdominal ultrasound guides embryo transfer catheter placement to improve implantation success rates. Additionally, ultrasonography plays a critical role in the early detection and management of ART-related complications, including ovarian hyperstimulation syndrome (OHSS), postretrieval hemorrhage, ovarian torsion, and pelvic infections. By integrating systematic imaging protocols and evidence-based practices, ultrasonography serves as a cornerstone of ART, ensuring procedural precision, optimizing therapeutic outcomes, and enhancing patient safety.