No single person invented English grammar. Grammar is the pattern of a language, and English had grammar long before anyone wrote a textbook about it. Speakers created and changed those patterns naturally over centuries.
What people often mean by this question is: who first wrote English grammar down? One important answer is William Bullokar, whose Pamphlet for Grammar appeared in 1586. It is often cited as the first printed grammar of English. Bullokar was not creating English from scratch. He was trying to explain how English worked, partly by borrowing ideas from Latin grammar.
Later writers also shaped the way English was taught. In 1762, Robert Lowth published a very influential grammar book. Some school rules that many people learned came from this tradition of prescription, which means telling people how they should write or speak.
English grammar includes patterns that native speakers use without thinking. For example:
- Statement: She writes clearly.
- Question: Does she write clearly?
- Verb pattern: I am, you are, she is.
These patterns were not invented by one author. They grew through everyday speech, writing, contact with other languages, and gradual change. Grammar books came later, as attempts to describe, teach, and sometimes control the language.