Ectopic pregnancy, defined as implantation of a fertilized ovum outside the endometrial cavity, represents approximately 2% of all pregnancies and remains a significant cause of maternal morbidity and mortality in early gestation. The majority occur within the fallopian tube, particularly the ampullary segment, though implantation can also occur in the interstitial portion, cervix, cesarean scar, ovary, or abdominal cavity. Early and accurate diagnosis is crucial to reduce the risk of tubal rupture and life-threatening hemorrhage. Transvaginal ultrasonography, with its superior resolution compared to transabdominal imaging, is the primary diagnostic modality, enabling assessment of intrauterine versus extrauterine implantation and embryonic viability. Serum β-hCG measurements serve as an essential adjunct, particularly when levels surpass the discriminatory threshold without visualization of an intrauterine gestational sac. Characteristic ultrasonographic findings include the tubal ring sign, complex adnexal masses, hemoperitoneum, and secondary changes in the endometrium such as decidual cysts or pseudogestational sacs. Recognition of these patterns is essential for differentiating ectopic pregnancy from early intrauterine gestation and other mimics. Unusual implantation sites, including cornual, cervical, and scar pregnancies, pose unique diagnostic challenges due to their potential for catastrophic bleeding. Although surgical confirmation remains definitive, advances in imaging have facilitated earlier diagnosis and enabled nonsurgical approaches such as methotrexate therapy. This chapter reviews the epidemiology, diagnostic strategies, and sonographic features of ectopic pregnancy, emphasizing the role of transvaginal ultrasound and serologic testing in guiding timely and effective clinical management.