The perils of prepositions: why "despite of" doesn't fit

What kind of error is it?

Grammatical error

Why do people make this mistake?

People often confuse similar expressions and attempt to use "despite" in the same way they use "in spite of", leading to the erroneous combination "despite of".

What is correct?

"Despite" is a preposition that should be used without "of". The correct expression is either "despite" or "in spite of".