杞人忧天，是汉语成语，读音是qǐ rén yōu tiān，意思是总是去忧虑那些不切实际的事物。杞人忧天是《列子·天瑞》篇中的一则寓言，后来成为一个固定成语，常用来讽刺那些不必要的担心，但也有人用其表达一种忧患意识。
To worry about the sky is a Chinese idiom with the pronunciation of qǐ rén yōu tiān, which means to always worry about those unrealistic things. Worrying about the sky is a fable in “Liezi Tianrui”, which later became a fixed idiom, often used to ridicule those unnecessary worries, but some people use it to express a sense of worry.
故事全文：
杞国有个担忧天地崩塌陷落之后身体没有地方寄托，睡不着觉吃不下饭的人。
又有为他的忧虑而担忧的人，因此去开导他，说：“天，只是聚积的气体罢了，没有地方没有气体。你伸展四肢，活动呼吸，整天都在天空中活动，为何担忧(天)崩塌坠落呢？”
那人说：“天如果是气体，日、月、星、辰不应当坠落下来吗？”
开导他的人说：“日、月、星、辰也是气体中会发光的东西，即使坠落下来，也不能对你造成伤害。”
那人又说：“那地崩塌了怎么办？”
开导他的人说：“地，聚积的土块罢了，充满了四方，没有地方没有土块，你踩踏(在上面)，整天都在地上活动，为何担忧地崩塌呢？”
（经过这个人一解释）那个人消除忧虑，非常开心；开导他的人也消除忧虑非常开心。
Full story:
There is a man in Qiguo who is worried that after the world collapses, there is no place for his body to sustenance, and he cannot sleep and eat.
There are people who are worried about his worries, so he went to enlighten him, saying: “Heaven is just a gas accumulation, there is no place where there is no gas. You stretch your limbs, move your breathing, and move in the sky all day. Why are you worried? What about the collapse and fall?”
The man said: “If the sky is gas, shouldn’t the sun, moon, stars, and stars fall down?”
The person who enlightened him said: “The sun, the moon, the stars, and the stars are also things that glow in the gas. Even if they fall, they cannot cause you harm.”
The man said, “What should I do if the land collapses?”
The person who enlightened him said: “The ground, the accumulated clods, is full of all directions. There is no place where there are no clods. If you step on (on it) and move on the ground all day, why do you worry about collapsing?”
(After an explanation by this person) that person is very happy to eliminate worries; the person who enlightened him is also very happy to eliminate worries.