Can a marketer be a co-founder without technical skills?
Short answer
Yes, and it is one of the more common founding pairs in software. The constraint is not technical ability, it is whether you own a function the company would otherwise have to hire for. A marketer who can independently produce demand is filling a role that is genuinely half the business. A marketer who can only produce plans that someone else must execute is not.
The longer version
Yes, and the pairing has a long history — plenty of well-known software companies were a builder and a seller. The question worth asking is not whether you can write code, it is whether you own a function the company would otherwise have to pay someone else to do.
That distinction matters more than it sounds. A marketer who can independently produce demand — who can take a product and, without anyone else's help, get it in front of the right people and convert them — is doing half the job. A marketer who produces strategy documents that a developer then has to execute has not removed work from the company, they have added a dependency.
The practical test before you approach anyone: can you point at something you got moving on your own? A newsletter you grew, a launch you ran, a community you built, traffic you earned. Not a campaign you contributed to inside a large team, where the brand did most of the work. Something where the audience arrived because of you specifically.
The full argument, with the rest of the picture around it:
Your Marketing Career Was Training For This