I've just come to terms with being transgender. How do I come out to my girlfriend of many years?

Honestly is always the best policy. It might seem harsh but if she doesn't accept you for who you are, then she isn't worth any more of your time. Simply sit down and tell her, remember to be completely honest, as long as you trust her.

Be honest with her; tell her the whole story. Be clear on what you want from this point on, and be patient in having this conversation with her. This might be overwhelming for her (maybe for you too), but just listen to each other, understand that this might need time, and be truthful.

Firstly, congratulations! Coming to terms with your true gender is an incredibly hard thing to do, and the hardest step is accepting it in yourself. Coming out is almost always difficult. You know your girlfriend better than any of us do, but I would recommend honestly above all else. Perhaps you can begin, not by flat out stating that you are transgender, but just by mentioning that you have been having certain feelings lately, and try to ease her into the idea rather than telling her all at once. Be prepared for a variety of reaction and questions. She will probably ask you a lot and you need to be prepared to give honest answers.

Ask her if she knows anyone who is transgender/supportive. If she really loves you, she'd understand.

Hi, I understand this is a very hard topic. Even though this may be difficult. I believe this will lead you to being happy and as your best self. Start small, slowly present the idea to her. Then, if it's to hard to say out loud, write her a letter or even on a sticky note. After you do give her a while to proceed it. You've been thinking about this for years and she just found out. Then if she really does love you, I think she'll accept you for who you are.

When I came out to my girlfriend after finding out I was non-binary, I broke the news to her in a subtle but honest way. Avoid sugar coating, avoid stalling. Give her plain fact, so that there's no room for misinterpretation. If she understands you and trusts you enough, she won't hold it against you or judge you for it, but be sure to give her some time to process the news.

It'd probably be good to see if you can learn her stance on the trans community with questions about what she thinks about some recent trans-centric news. (Like that school that made trans students wear green wristbands for identification) Then if you ask her hypothetical questions about how she would feel if her partner was trans and it all seems well, it should be relatively safe to out yourself to her.

i would first randomly ask how she would've reacted when you guys met if you were the opposite sex and observe the reaction

To be straight, you should just be open about the situation don't hide anything go slow but be very honest.

Honestly, you have to come out to her. This is who you are. she can't stop you from being yourself. I'm sure she can come to terms with it.