The noun 国王 (guówáng) means "king" and refers to the male sovereign ruler of a kingdom. It combines 国 (country/nation) with 王 (king/ruler). It is used in historical contexts, fairy tales, and when discussing monarchies.
国王住在山顶上的一座大城堡里。
Guówáng zhù zài shāndǐng shàng de yī zuò dà chéngbǎo lǐ.
The king lives in a large castle on the mountaintop.
那位国王非常爱护自己的百姓。
Nà wèi guówáng fēicháng àihù zìjǐ de bǎixìng.
That king cares deeply for his people.
故事里的国王派勇士去消灭森林中的怪兽。
Gùshi lǐ de guówáng pài yǒngshì qù xiāomiè sēnlín zhōng de guàishòu.
In the story, the king sent warriors to eliminate the monster in the forest.