"Our message to the world will be this: you cannot obtain legal status or become a citizen of the United States by illegally entering our country," he said in a speech in Phoenix as he laid out a tough, 10-point plan to crack down on illegal immigration.
"You can't just smuggle in, hunker down and wait to be legalized," Trump added. "Those days are over."
The fiery speech confirmed Trump's hard line on immigration just hours after he met in Mexico with President Enrique Pena Nieto and insisted he would order that a giant wall be built on the US-Mexico border if he is elected.
The billionaire candidate's plan includes deporting immigrants with criminal records, cancelling President Barack Obama's executive orders protecting millions of undocumented migrants, and blocking federal funding to so-called "sanctuary cities" that bar discrimination against undocumented workers.
While he insisted, as he regularly does on the campaign trail, that Mexico will pay for the wall, Trump said in Mexico that he and Pena Nieto did not discuss who would fund the construction.
But Pena Nieto contradicted Trump by tweeting that he told the Republican nominee in their meeting that Mexico would not pay for such a wall.
"At the start of the conversation with Donald Trump I made it clear that Mexico will not pay for the wall," Pena Nieto wrote after Trump departed Mexico City for Phoenix.
In his speech, Trump laid out a grim, sweeping plan to dramatically slash illegal immigration, a main plank of his presidential campaign.
"Our enforcement priorities will include removing criminals, gang members, security threats, visa overstays, public charges -- that is those relying on public welfare or straining the safety net along with millions of recent illegal arrivals and overstays who have come here under this current corrupt administration," he said.
Trump demanded an end to what he called "catch-and-release" programs along the country's southern border, enforcement of existing immigration law, and "zero tolerance for criminal aliens."
Seeking to end his ambiguity on his immigration positions, he said he would be "fair, just and compassionate" in his plan.
But he remained unclear on exactly what would become of the 11 million people currently living in the shadows, other than to suggest they would need to leave and come back legally if they wanted legal status.