Pigs are one of the largest scale livestock species globally. In large-scale pig farms, the reproductive management of gilts and sows is a critical control point to ensure production capacity and reduce costs. More precisely, the understanding the developmental status of ovarian follicles in pigs is a critical basis for developing and improving management programme of oestrus detection and artificial insemination, a core component that determines sow production performance, but this knowledge is largely lacking. Ultrasound scan is a non-invasive and convenient method to understand the follicular developmental statues. However, there is currently a lack of reliable data to establish imaging standards, making it difficult to provide the most accurate support and reference for reproductive management in pigs. This dataset contains 868 images of ovarian follicles at different developmental stages in gilts and sows in favour of the identification and understanding of sow reproductive condition. To our knowledge, it is the inaugural dataset containing ultrasound images of large animals.