An audio captioning dataset is a structured collection of audio recordings paired with corresponding natural language descriptions that explain the auditory content, acoustic environment, and sound events present in each clip. Unlike speech recognition datasets that transcribe spoken words or audio classification datasets that assign discrete categorical tags, an audio captioning dataset provides free-form sentences capturing the contextual relationships, physical characteristics, and temporal progression of sounds. These datasets, which are compiled through human annotation, expert curation, or automated generation pipelines using foundation models, serve as fundamental resources for training and evaluating machine learning models on tasks such as automated audio captioning, audio-language retrieval, and multimodal audio-visual understanding.