A MajorMode for editing Ada programs comes with Emacs.
Project page:
The current ada-mode maintainer is StephenLeake?,[1] who maintains the code in GNU Emacs and periodically publishes updated versions on the project page.
The ada-mode distribution contains gpr-mode.el, a major mode for editing GNAT project files (.gpr).
ElseMode comes with templates for writing Ada source code.