HerdNet is a deep learning-based aerial animal detection and counting system tailored for wildlife and livestock monitoring. It processes high-resolution imagery to identify and count herds using object detection models trained on diverse habitats like savannas and deserts. The system supports bounding box annotation formats, pretrained models, and reproducible pipelines via conda environments. Originally developed for academic research, it has been applied to species including buffalo, elephants, and goats using aerial and drone imagery.