Converting Windows app to Mac app?

Are there any software or hardware solutions that enable a person
(like myself) to convert a Windows executable file (created in Delphi)
to a file which will run on the MacIntosh platform?  Or... is it necessary
to rewrite the entire program with Mac-based development software?

Any comments on this are welcome (and much needed).  Thank you very much!

Joseph Emanuel
jeman...@bright.net