Do i need a passport to travel to dublin from glasgow by coach?

You require standard photo ID. Unless you are a non-national living in Ireland under a permit / visa. Drivers license will be fine.

If you are on the ferry then you should be ok with your driving licence if you have the photo id one. We travel between Holyhead and Dublin on a yearly basis and although we always take them, we have never been asked to show our passports yet, they do however have our travel documents with names, home address, and car rego on them. If you are truly unsure of what id will be acceptable then the best people to contact are the coach company, or the ferry provider themselves...just to put your mind at rest! Have a great time in Ireland.

you might not need one if you get the ferry to Scotland, then get the coach but if your flying over you will probably need one. You could apply for an emergency passport, it might get to you in time.

i assume those two cities are in different countries, so yes. they wont let you leave the airport without getting your stuff checked. are you sure you cant get one? i think mine took less than a month to arrive and you might be able to pay to get one faster than standard time.