The Short Answer
Megan doesn't have a traditional Gaelic equivalent, but there are two valid ways to handle it depending on which Gaelic language you're working with. In Irish (Gaeilge), Megan is typically rendered as Méigéan or simply kept as Megan. Some people use Míonáin as a poetic adaptation, though that's more of a stretch and not something you'll see in official documents. In Scottish Gaelic (Gàidhlig), you'd likely see it spelled Meagann or left as Megan. Scottish Gaelic tends to be more straightforward about borrowing names without heavy modification.
How Do You Say Megan In Gaelic?
The honest answer is that neither language has a native Megan, so any version you use is an adaptation. That's the reality of modern naming conventions in Celtic languages. If you're filling out paperwork for someone who identifies as Megan, writing it as Megan is usually the safest move. Neither the Irish Passport Service nor the National Records of Scotland is going to reject it. Megan is a diminutive of Margaret, which comes from the Greek word for pearl. In Irish, the traditional equivalent of Margaret is Máiréad. That's the name you'll see on birth certificates going back decades. It's pronounced roughly "MAY-ray" in English and follows Irish orthography rules pretty closely. So if someone named Megan asks for their name in Irish, Máiréad is the most defensible translation. It's not phonetically close to Megan, but it's semantically accurate since they're the same root name. I ran into this exact problem a few years ago when helping a friend update her health records. She had been legally Megan for her whole life but her mother's side of the family was Irish. She wanted her medical forms to include the Irish version. The clinic asked for consistency between legal documents and translated identifiers. We ended up listing both — Megan and Máiréad — on the form with a notation. It worked, but it added about twenty minutes to the intake process because the receptionist wasn't familiar with having dual-name entries. Not a big deal, but worth knowing if you're doing this for official purposes.
Scottish Gaelic vs Irish Gaelic
People often conflate these two languages as if they're interchangeable. They're not. A name that works in Irish might look completely foreign in Scottish Gaelic and vice versa. The orthographic systems overlap somewhat, but the phonological rules differ enough that direct transliterations don't always land well. If you're Scottish and someone asks how Megan looks in Gàidhlig, Máiréad isn't really the go-to there. You'd more likely see Meagann or just Megan. Scottish Gaelic tends to preserve the original form of borrowed names rather than find a traditional equivalent. Irish has a stronger tradition of Gaelicising foreign names, partly because the language revival movement put more systematic effort into that practice.
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Common Pitfalls
The biggest mistake I see people make is trying to phonetically spell Megan using Irish orthography rules and ending up with something that looks like Méagán or Megáin. Those are recognizable attempts but they're not standard. Irish orthography has specific rules about broad vs slender consonants and vowel combinations, and getting them wrong makes the name look like a tourist wrote it. That matters if you're putting this on a tattoo, a piece of jewelry, or a formal document — people who know the language will notice. Another issue is assuming that because a name has a "Gaelic version," it automatically carries cultural legitimacy. It doesn't. A phonetic rendering of Megan in Irish spelling isn't the same thing as adopting a traditional Irish name. The difference matters to native speakers and to anyone checking your work against a dictionary.
What I'd Recommend
If you need this for a legal or official context, use the name as it appears on your documentation and add the adapted form in parentheses if you want both. Máiréad is the meaningful Irish equivalent if you're going that route. Meagann or Megan works for Scottish Gaelic. If you're just curious or want it for personal use, go with whichever version sounds right to you and check it against a reliable source like focus.ie for Irish or www.gaelic.co.uk for Scottish Gaelic before committing to anything permanent.