The 25-year-old had virtually secured the victory on Saturday after getting help from his Astana team-mates in the mountains to beat Dutchman Tom Dumoulin and take the lead ahead of the flat final stage arriving in Madrid.
Aru crossed the line alongside his team-mates at the end of the 98.8-kilometre (61.4-mile) stage through the streets of the Spanish capital, then gave a broad smile and lifted his right arm into the air to celebrate his first major victory.
“I have to thank all of my team-mates,” Aru said. “This victory is for them. They did a fantastic job. They deserve all the credit for helping me earn this victory.”
In 2014, Aru finished fifth in the Vuelta and third in the Giro d’Italia, while this season he had to settle for second place in the Giro behind Alberto Contador.
“This is a dream come true for me after such a stressful event,” said Aru, whose major triumphs so far had been victories in two Vuelta stages and three Giro stages.
Joaquim Rodriguez of Spain, who recovered from a blown tyre halfway through the final stage, finished second overall, 57 seconds behind Aru. Rafal Majka of Poland was third, more than a minute back.
Colombian Nairo Quintana finished fourth overall and countryman Esteban Chaves fifth. Dumoulin was only sixth after losing ground on Saturday. John Degenkolb of Germany was perfect on the final sprint in Madrid to secure his first stage victory.
Only an injury or an unforeseen incident could have kept Aru from winning the title yesterday. He had secured a comfortable lead in the 176-km (109-mile) mountainous stage from San Lorenzo de El Escorial to Cercedilla on Saturday. He surged past Dumoulin on one of the ride’s climbs to take a commanding advantage over the Dutchman, who had earned the red jersey in Wednesday’s time trial.
Aru wasn’t even Astana’s top rider at the start of the three-week event. He only came into contention after team leader Vincenzo Nibali was expelled from the race for holding on to a team car while trying to make up lost time after an accident in the second stage.