Is it haram to sleep on my stomach?

No, it's not haram. A hadith says Allah doesn't love that way of lying down, so most scholars call it disliked (makruh), not forbidden. The recommended way is to sleep on your right side. And whatever position you roll into while you're asleep doesn't count against you.

What the hadith says

The Prophet Muhammad ﷺ once saw a man lying on his stomach and said, "Indeed, such lying down is not loved by Allah" (Jami' at-Tirmidhi 2768, graded hasan).

Because of this, most scholars say lying face-down is disliked, especially without a reason. "Disliked" means you're rewarded for avoiding it, but you're not sinning if you do it. Some versions of this narration also have weaker chains, which is another reason scholars don't go further than "disliked."

The recommended way: right side

The Prophet ﷺ told a companion: "Whenever you go to bed, perform wudu like you do for prayer, then lie on your right side" (Sahih al-Bukhari 247), followed by a short prayer before sleeping. See Can I sleep with my feet pointing toward the Qibla?

You don't have to stay on your right side all night. Starting the night that way is the sunnah.

What if I roll over in my sleep?

That's not on you. The Prophet ﷺ said that three people's actions aren't recorded, and the first is "a sleeper till he awakes" (Sunan Abu Dawud 4403). You're only responsible for how you choose to lie down, not where your body ends up at 3 a.m.

Is sleeping on my back or left side okay?

Yes. Only lying face-down is mentioned as disliked. Sleeping on your back or your left side is completely fine.

And babies are a separate case. Follow your pediatrician's safe sleep advice, which today usually means putting babies to sleep on their backs. The hadith is about adults choosing how to lie down. See Is it haram to sleep naked?

Medical reasons

If you have back pain, a breathing issue, or your doctor tells you to lie face-down (for example after some eye surgeries), follow your doctor. Islam never asks you to harm your body.

لَا يُكَلِّفُ ٱللَّهُ نَفْسًا إِلَّا وُسْعَهَا "Allah does not burden a soul beyond what it can bear." Quran 2:286

Key points

Sleeping on your stomach is disliked, not haram.
The sunnah is to start the night on your right side.
Rolling over while asleep doesn't count.
Medical needs come first.

Tip: Build a simple bedtime routine: wudu, lie on your right side, and a short du'a. Start with just the right-side habit and add the rest later.