Which wrist should Muslims wear a watch on?

No specific sunnah for watches

Watches are a modern item, so there's no direct instruction about them. Scholars look at related evidence instead. The Prophet ﷺ liked to start with the right side in good things: putting on shoes, combing his hair and purifying himself (Sahih al-Bukhari 168). Based on this general love of the right, some scholars say wearing a watch on the right wrist is a little better.

The ring comparison

Other scholars compare a watch to a ring, the closest thing to it in the Sunnah. The Prophet ﷺ is reported to have worn his ring on his right hand in some narrations (Sahih Muslim 2094) and on his left in others. Scholars concluded that both hands are fine for a ring, so both wrists are fine for a watch too. Many scholars say the matter is wide and a person should do what is easiest.

Practical reasons are valid

• Most right-handed people wear a watch on the left so it doesn't get in the way when writing or eating.
• Smartwatches and fitness trackers often work best on your non-dominant hand.
• Left-handed people may prefer the right wrist for the same reasons.

Choosing a wrist for comfort isn't against the Sunnah. It's simply a worldly matter where Islam gives you freedom. For the right hand rule that really does apply, eating and drinking, see Do I have to eat with my right hand only?

What actually matters

• Gold watches: most scholars say men shouldn't wear solid gold watches, just like gold rings. See Can Muslim men wear gold rings?
• Wudu: water must reach the skin under the strap when you wash your arms. Slide the watch up or take it off. See What breaks wudu?
• Prayer: avoid checking your watch during salah, since it distracts from your focus.