Can Muslims believe in ghosts?

Where do souls go after death?

When someone dies, their soul is taken by the Angel of Death and enters the barzakh, the in-between stage that lasts until the resurrection. The Quran describes a person at death asking to go back and do good, and the answer is no:

So the dead don't haunt houses, finish "unfinished business", or come back to warn relatives. Their soul experiences either comfort or hardship in the grave, which is a different world from ours. See What happens in the grave in Islam?

Then what are people seeing?

Islam doesn't deny that people sometimes have strange experiences. Possible explanations include:

• Jinn. They are real, live alongside us, can see us when we can't see them (Quran 7:27), and may sometimes appear in other forms. Scholars say a "ghost" that imitates a dead person is, at most, a jinn, not the person.
• Ordinary causes. Old houses creak, the brain fills in shapes in the dark, and sleep paralysis can feel very real. Most "haunting" stories end here.
• Grief. Sensing a loved one near you after their death is a common and natural part of mourning, not a visit from their spirit.

Can the dead hear or know about us?

Scholars discuss this. There are narrations about the dead hearing the footsteps of those leaving the funeral, and the greeting of visitors to graves, and the details are debated. But none of this means the dead return to this world or can be contacted. Our link with them is dua, charity on their behalf and visiting their graves. See What do Muslims believe happens after death?

What if my house feels "haunted"?

Don't call a medium or ghost hunter. Recite Surah al-Baqarah or Ayat al-Kursi in the home, say "Bismillah" when entering, and keep up your adhkar. The Prophet ﷺ said Satan flees from a house in which Surah al-Baqarah is recited (Sahih Muslim 780). Check practical causes too, and if fear is affecting your sleep or mood, talk to a doctor. See Can I play the Quran in my house for protection?