Yes, we do, but we do not all believe in God in the same way. All Stoics are pantheists, because Nature is our god, literally, but you can be an atheist or a deist or an agnostic and still be a Stoic in good standing. The key to what kind of Stoic you are depends on whether you believe that the intelligence and processes of Nature are conscious or unconscious. Is Nature conscious or unconscious? Human beings were created by Nature and have consciousness. Are we the only ones, or is our creator also conscious?
The early Stoics believed that Nature was both providential and conscious. These were the deists, but when Stoicism was adopted in ancient Roman there were a few who believed that Nature was unconscious. These were the first Stoic atheists. Today we have Stoics who are deists, atheists, and agnostics. Such diversity is perfectly acceptable. The Stoic community has a large tent, and we are tolerant of disagreement within it.