Story completion is a natural language processing task in which a computational model is given an incomplete narrative prefix and must generate or select the most plausible, logically consistent continuation or ending. Commonly used as a benchmark for language models, the task evaluates an artificial intelligence system's capacity for narrative comprehension, commonsense reasoning, and causal inference. Rather than assessing simple lexical pattern matching, story completion tests whether a system can track narrative structure, understand real-world cause-and-effect relationships, and resolve ambiguous contexts to produce coherent outcomes.