The ex-Sec. of State -- and one-time presidential candidate -- just tweeted about the hotly-debated nominations heard around the world Tuesday ... and she's in the camp that this was an egregious snub from Academy members ... especially in light of Ryan Gosling's nod.

HC wrote, "Greta & Margot, While it can sting to win the box office but not take home the gold, your millions of fans love you. You’re both so much more than Kenough."

She also threw in her own little fun hashtag to cap off her point, adding ... "#HillaryBarbie."

Hillary is just the latest person to slam the non-nominations -- remember, Ryan himself actually denounced the fact his costar/director didn't receive recognition ... even though he himself got a Best Supporting Actor nomination.

He said, "No recognition would be possible for anyone on the film without their talent, grit and genius. To say that I’m disappointed that they are not nominated in their respective categories would be an understatement." Likewise, he also praised America Ferrera's nom.

Speaking of America ... she, too, slammed Margot and Greta's exclusion -- just piling on top of the collective outrage most of the Internet has been expressing over the past 24 hours.

Margot and Greta haven't said anything about it themselves ... but people have their backs.

Fun fact about the Academy's makeup as of last year -- it looks like 33% of voting members are women or female-identifying ... so yes, there does seem to be more guys than gals. Hard to say if that's behind these two not getting selected or not ... but it is interesting.