The Stanford Named Entity Recognizer (NER) is a natural language processing tool developed by the Stanford NLP Group. It identifies and classifies named entities in text into predefined categories such as persons, organizations, and locations. This helps in extracting meaningful information from unstructured data. The NER is part of the Stanford CoreNLP suite, which provides various linguistic analysis tools. It uses machine learning techniques to improve accuracy and can be trained on custom datasets. The tool is widely used in applications like information retrieval, content classification, and data mining.