Formal:
* Omulimu gwa ssanyu okukulaba: (Literally: "It's a pleasure to see you") This is the most formal way to say "Welcome."
* Mwagalwa okusangibwa wano: (Literally: "You are welcome to be here") This is also a formal way to say "Welcome."
Informal:
* Osannyu okuba wano: (Literally: "You are happy to be here") This is a more casual way to say "Welcome."
* Osiimye okuba wano: (Literally: "Thank you for being here") This is a more casual way to say "Welcome."
You can also simply say:
* Welcome (pronounced "we-come" in Luganda) This is a widely understood word in Luganda.
The best choice will depend on the specific situation and your relationship with the person you are greeting.