In Mandarin we will say it : "国际水平的"， “世界级的”. You can take it as an adjective,which means the thing it modifies has a quite high level, and is world-famous. In Chinese the word "world-class sporting event" is "世界级体育赛事" or "国际体育赛事"， like the Olympic games or the Boston Marathon, etc. And "world-class tennis player" means "世界级网球运动员／选手"， for example Rafael Nadal and Roger Federer. Hope it can solve your problem :D

世界级

World-class in english = 世界级 in chinese