“萬無一失”，漢語成語，比喻十分穩妥，絕對不會出差錯。可以翻譯爲“guarantee complete success; no risk at all; nothing will go wrong; perfectly safe”等。
例句：
由他掌舵，通過這段激流險灘是萬無一失的。
With him at the helm, we are a hundred percent safe crossing these treacherous rapids.
爲確保萬無一失，一架警用直升機一直在空中警戒。
To make extra certain, a police helicopter kept watching from the sky.