I just preordered the iPhone 11. Does it come with a warranty?

Yes, it comes with a warranty but there are restrictions and it is worth the time it takes to read the documentation:

About your support coverage and service options - https://support.apple.com/en-us/HT202696

http://www.apple.com/legal/warranty/products/iphone-english.html

Extended warranties are also available:

Applecare+ for iPhone

https://www.apple.com/support/products/iphone.html

all products come with warranties it's not up to the producer but the law of the country

Legal - Hardware Warranties - Apple

more

https://en.wikipedia.org/wiki/Warranty