Background: This study aims to evaluate pregnant women’s knowledge of antenatal ultrasound in Saudi Arabia and its correlation with demographic factors like age and education to enhance prenatal care. Methods: A cross-sectional study was conducted in six Saudi Arabian hospitals, involving 22 questions split between sociodemographic information and knowledge of antenatal ultrasound. Descriptive statistics were used to characterize the participants’ demographics and responses. Additionally, inferential statistics were employed to analyze the relationships and differences among the study variables. Results: Among the 531 pregnant women in the study, most demonstrated a good understanding of antenatal ultrasound, identifying its various uses. Specifically, they recognized its roles in evaluating fetal growth (82.5%), placental location (81.7%), amniotic fluid volume (67%), and fetal morphology (65%), predicting the delivery date (79%), and determining the baby’s sex (89%). A majority viewed ultrasound as important (89.3%), safe (82.3%), and tolerable (76.3%) for prenatal care. Additionally, 66.7% felt adequately informed, mainly through clinical staff and doctors. Younger age, lower education, lack of prior ultrasound experience, and first pregnancy were linked to lower knowledge. Approximately 65% were uncertain about the nonionizing radiation properties of ultrasound. Conclusions: The study found that while most pregnant women in Saudi Arabia understand the objectives of antenatal ultrasonography, there are gaps in their knowledge about its nonionizing properties. Younger age, lower education, lack of prior ultrasound experience, and first pregnancy contribute to lower knowledge.