All’s fair in love and war 是個諺語，意為「在情場和戰場上可以不擇手段」。這個諺語自 1579 年以降一直有不同的寫法，如 All’s fair in love and war and an election year (在情場和戰場上以及選舉年可以不擇手段)、All’s fair in love and war and politics (在情場、戰場和政治上可以不擇手段) 或者 All’s fair in love and tennis (在情場和網球場上可以不擇手段)。
現今的寫法或說法似乎可以追溯到 1789 年出版的一本作者不詳的小說《The Relapse》(Or, Myrtle-Bank)：”Tho’ this was a confounded lie, my friend, ‘all is fair in love and war’… “。
例句：
- Peter had to flatter his boss in order to get that big promotion. All’s fair in love and war, right? (彼得為了獲得那個重大的升遷，不得不對他的老闆逢迎拍馬。在情場和戰場上可以不擇手段，對吧？)
- I cheated on the entrance exam, but I really want to get into that school. All’s fair in love and war. (我在入學考試作弊，但我真的很想進入那所學校。在情場和戰場上可以不擇手段)
- To get Mary to go out with me, I lied and told her that her boyfriend was seeing another woman. All’s fair in love and war. (為了使瑪麗跟我交往，我騙她說她男友正和另一位女子拍拖。在情場和戰場上可以不擇手段)