《当你老了》是爱尔兰诗人威廉·巴特勒·叶芝（William Butler Yeats）创作的一首著名抒情诗，这首诗充满了对爱情的深情与怀念。以下是这首诗的原文：
When You Are Old
When you are old and grey and full of sleep,
And nodding by the fire, take down this book,
And slowly read, and dream of the soft look
Your eyes had once, and of their shadows deep;
How many loved your moments of glad grace,
And loved your beauty with love false or true,
But one man loved the pilgrim Soul in you,
And loved the sorrows of your changing face;
And bending down beside the glowing bars,
Murmur, a little sadly, how Love fled
And paced upon the mountains overhead
And hid his face amid a crowd of stars.
这首诗以温柔而感人的语言描绘了诗人对爱人青春年华的回忆以及他对她永恒之爱的承诺。诗中提到，当她年老时，头发灰白，坐在炉火旁打盹，翻开这本诗集时，会想起年轻时那双充满魅力的眼睛。虽然许多人曾爱过她的美貌，但只有一个人真正爱她的灵魂，即使在岁月的变迁中，她的容颜发生了变化，这份爱依然不变。
这首诗表达了深刻的情感和对真爱的追求，成为经典的爱情诗歌之一。它提醒我们珍惜当下，因为时间会改变一切，但真挚的感情却能经受住时间的考验。