This phrase is a notorious slogan found on stickers and T-shirts, used by people who oppose the policies of George W. Bush. The sticker also features a picture of W. The slogan is an anthem of resistance and refusal to accept Bush as America's legitimate President. It became more commonplace after the Iraq war started.
At the parking lot of a Media Play store I saw a purple car with a Not My President sticker on the rear.
by I Saw U2 Live Twice September 19, 2007
"Not My President" is a slogan commonly used to describe a metaphor. The President of the United States of America is factually the president. However, when people use the slogan "Not My President," they are referring to their individual vales which the current president does not represent.
Yes President Trump is literally my president, but Trump is a pathological liar, attempts to intimidate people over twitter like a "keyboard tough guy", has cheated on multiple wives - multiple times, doesn't know how to spell common words, is a massive bigot, a mild racists with a father that was a member of the KKK, extremely narcissistic with a petty childish demeanor, tremendously unjust, unforgiving control-freak with a vindictive personality that requires approval, a misogynistic, homophobic, unethical, megalomaniac, self-centered, egotistical, ignorant, incompetent, (etc.) and an embarrassment not fitting of a head of state. Trump is NOT MY PRESIDENT because he doesn't represent my values.
by Draxx them Sklounst August 4, 2018
As the election on Tuesday came to an end. The system chose the Donald as elect-president. The people chose Hillary. Trump protesters took to the streets to let everyone know, that he will not be their president.

Everyone else: NOT MY PRESIDENT

Ex2) Chloe: omg, these stupid Hillary supporters need to understand the we the people elected him. Donald is so hot
Jasmine: you mean, YOU racists bigots and the system elected him. I voted Hillary she won, therefore he is NOT MY PRESIDENT.
by Lilwiggle34 November 12, 2016
An utterly retarded term used by people with mental illness, if used in the United States of America people who say this term should be viewed as retarded and treated as if.
Person raised stupidly:Trump is Not My President
Person Raised Correctly: You are mentally ill.
by LinkinZeke February 21, 2017
A phrase you can use when you don't like the outcome of the situation you are in.

It works in so many ways. Especially if you sit in fetal position and squeeze your eyes shut really hard. Then yell it as loud as you can. That way you win.
Damien: I crushed you in that game of Halo the other really suck.
Brian: Not my president.
by cramagraham June 8, 2018
Highly controversial song put out by a 19 year old white kid from New York. While the argument is that its racist its the same structure as the my president is black for Obama.
by ktccasset January 24, 2009
When all you hear about on the news and social media is Donald Trump and you don't live in America.
I almost never hear about any of my own country's news. All the news has been is Trump this and Trump that and he's not actually my President.
by My Names Not Pachinko February 8, 2018