Derek Hough’s celebrating ‘Dancing with the Stars’ big 2-0 — which just so happens to line up with TMZ’s own 20th birthday — and he’s spilling the secret sauce that’s kept both of us swinging strong all these years!

The pro dancer helped us shake off the Monday blues … chatting at LAX about how both the dance competition and our celeb news site have kept fans hooked for years — thanks to one thing we share in common: authenticity.

Derek says people love a no-holds-barred look at others in totally different settings — and that’s exactly why both ‘DWTS’ and TMZ have thrived … keeping it real and raw, no filter needed.

Catch the full clip … ’cause Derek spills even more of ‘DWTS’ goodness, including his all-time favorite moment on the show, which involved the late, great Len Goodman.

Honestly, it’s a refreshing convo — and we’re pumped to be celebrating our 20th right alongside such massive pop culture powerhouses!