He isn't the first person to do so.
"America First" has been the name of at least two political groups in the past century, both of which focused their platforms on non-interventionist foreign policies.
Opposing World War II Intervention
The first iteration came in the 1940s with the America First Committee, which was formed largely in an effort to keep the United States out of World War II.
The committee chose to disband days after the Japanese bombed Pearl Harbor.
Circling back to Trump's "America First" speech today, he praised America's intervention in World War II.
"We have a lot to be proud of in the 1940s. We saved the world. The greatest generation beat back the Nazis and Japanese imperialists. Then we saved the world again. This time, from totalitarianism and communism, the Cold War. It lasted for decades, but guess what, we won and we won big," Trump said today.
The Current Political Party Bearing the Phrase
According to Jonathan Hill, the party's national chairman, they support "controlling our nation's borders, bringing back tariffs as opposed to free trade, and we're pretty much opposed to much of our foreign policy as it stands today."
The group is also socially conservative, but to an extent further than many of the Republican presidential candidates, as the America First Party "does not support abortion in all cases and they are opposed to homosexuality," Hill said.
At its peak, the group had state chapters in 47 states, "but at the present moment, we don't have many active state parties," Hill said.
The group has not run a candidate in the 2016 presidential race and has not endorsed any of the candidates, yet.
Hill said that he is "reserving my judgment on Donald Trump. ... But he does say a lot of the right words."
"He's an interesting candidate. He's shaking up the establishment," Hill told ABC News.