He'll take on Democrat Hillary Clinton in November's election.
The billionaire has told his party's convention in Ohio he will be the law and order candidate, and has promised to tighten up border controls.
Mr Trump's used his acceptance speech to again raise concerns about immigration.
If elected he said he'll suspend all immigration from countries that have been “compromised by terrorism”. He also reiterated his promise to build a wall on the border with Mexico to reduce illegal immigration.
