Go speak with a local attorney about a deed transfer.
Before you do so, however, it's important to recognize that when one adds a girlfriend or boyfriend to a deed, it can be very problematic if the home ownership lasts longer than the relationship.
Good luck to you.
Michael S. Haber is a New York attorney. As such, his responses to posted inquiries, such as the one above, are limited to his understanding of law in the jurisdiction in which he practices and not to any other jurisdiction. In addition, no response to any posted inquiry should be deemed to constitute legal advice, nor to constitute the existence of an attorney/client or other contractual or fiduciary relationship, inasmuch as legal advice can only be provided in circumstances in which the attorney is able to ask questions of the person seeking legal advice and to thus gather appropriate information.
You can transfer title (or any portion thereof) by either a general warranty deed, a limited warranty deed or a quitclaim deed. In your situation, a quitclaim deed should suffice.
You also need to consider how you want to hold title with your girlfriend; as either joint tenants with rights of suvivorship or as tenants in common. If you are tenants in common, should one of you pass away, that person's interest in the property will go into their estate, which would need to be probated to transfer the property interest. If you are joint tenants with rights of survivorship, should someone pass away, the title immediately transfers back to the survivor and probate can be avoided.
Keep in mind that just because you add your girlfriend to the title, that does not obligate her to your lender. For her to be legally responsible for the mortgage, the lender would need to modify your loan to add her to the note and security deed.
As my colleague pointed out, you need to really consider the situation and the consequences of adding your girlfriend to the title. If you break up (and there was no marriage) then if she is unwilling to transfer title back to you, you will need to go to court to get your property back. Also, if she has any outstanding judgments against her, they will attach to the property and will need to be paid off before you can sell or refinance the property.
Just to echo the other responses, yes, in a perfect world, you'd sign that quit-claim deed adding her to title and eventually y'all will get married. HOWEVER if ANYTHING goes sideways in the relationship and you two want to split up, she now has leverage over 'your' house if you wanted to keep it. Bottom line, you'd probably have to write her a check to remove her from title... This scenario happens all the time, so 'consider beware'! (and that scenario is the same whether you are both on title as boyfriend/girlfriend or husband/wife).
Kudos on trying to be honorable though; as Beyonce says, 'put a ring on it' and move forward from there! Sorry, couldn't resist. Good luck!
Call Rob Coats or Randy Cordle at 770-577-7155. Their office is on bankhead right down from Gumbeauxs. They can do a quitclaim deed for you at a very reasonable rate.
However, pay special attention to the other answers you have received here. Be certain this is something you are sure about, because it will be one very hairy beast if you become unsure later.