不明確なツバメの速度は、明確に定義された、科学的に研究された量ではなく、映画「Monty Python and the Holy Grail」で、回答が困難な質問へのユーモラスな言及として有名です。ただし、さまざまな種類のツバメの飛行速度に基づく大まかな推定値は、時速20〜60マイル（時速32〜97キロメートル）の範囲です。
The speed of an unladen swallow is not a well-defined or scientifically studied quantity, and is famously mentioned in the movie "Monty Python and the Holy Grail" as a humorous reference to a difficult-to-answer question. However, rough estimates based on the flight speeds of different species of swallows can range from around 20 to 60 miles per hour (32 to 97 kilometers per hour).