I live in New Jersey and am buying insurance through the healthcare.gov marketplace. Some of the plans are marked 'HSA'. Can I purchase these plans even if I don't have a health savings account? (HealthCare.gov's customer service was unable to answer this question.)
Having an HSA-eligible plan means that you are legally ALLOWED to open an HSA. You are not required to do so. Or if you do open one, there is no law requiring you to make any minimum contribution to it. (The bank that manages the HSA might have minimum deposits, but these are usually small.)
That said, it is to your advantage to open an HSA. This allows you to pay your medical bills with tax-free money. The higher your medical bills and the higher your tax bracket, the better this is for you. If you don't see any need to open an HSA, I think in most cases you would be better off to get a non-HSA medical plan. But without knowing the details of the plans available to you, I can't really say.
Additional thought that occurred to me: It's illegal to open an HSA if you don't have an HSA-compatible plan. If you switch from an HSA-compatible plan to a non-HSA plan, you can keep an existing HSA and you can make disbursements from it but you can't make deposits to it. Anyway, my point being, most people who buy an HSA-compatible policy won't already have an HSA, and it would be illegal for them to have one. (Unless they had previously had an HSA-compatible plan.) So the situation is rather the opposite of what you're asking: It's not that you have to get an HSA before you can buy an HSA plan. You have to get the insurance plan first, then open the HSA.