There is of course the academic/teaching route but there would also be paths into accountancy, engineering and being an actuary but if it's a good degree a lot of companies would hire you in fields that aren't enormously related.
I see, in terms of careers for maths PhDs, aside from the roles noted above depending on the nature of your PhD project (e.g. how much programming/computational work was involved), there may also be roles in data science, quantitative finance, or software development/engineering. There will also be lots of less directly relevant roles in e.g. the civil service etc, and having a PhD might allow you to apply for certain higher entry positions depending on your experiences within your PhD (e.g. whether it involved any management of other people in the process).