I believe it is Cosmos bipinnatus.

Yes it is a Cosmos, definitely not a weed. It should flower profusely all summer. If you have the right conditions it could easily self sow, perhaps from a neighbour's plant, for example. Lucky you, I have to buy them as small plants each year as conditions here aren't good for growing them from seed. They are treated as annuals, as they are tender. They also come in white & carmine.

Thank you both so much! It must have come over from a neighbour as you said!

Yup cosmos! One of my favorite annuals, they do well in iffy soil and just keep going. Mine get 2 feet or bigger.