BASIC on an Apple ][+
Cause I'm old. https://t.co/i9zp1fhOT5

— Dogs Don't Have Thumbs (@MorlockP) October 8, 2019

Mine was Level I Basic, a Tiny Basic derivative, on the TRS-80, approximately 1981. The first program I wrote was something like:

10 PRINT MY NAME IS MIKE
20 GOTO 10

To be fair, I was five years old.