Djokovic is chasing a record seventh title but again found the 20-year-old Rune, who is making his debut at the eight-player event, a troublesome opponent before pulling off a third win in five meetings.
It was past midnight in Turin when Djokovic completed a 7-6 (4), 6-7 (1), 6-3 victory after three hours and four minutes on court.
Rune has fared much better against Djokovic than most of his rivals over the last couple of years, beating him in Paris last autumn and Rome in the spring before a narrow defeat in the French capital a week-and-a-half ago. The Serb went on to win the Masters series title, maintaining his record of not having lost a match since the Wimbledon final.
Djokovic told Prime Video: “It took everything. I saw in the first game when he fired shots from the baseline, I knew it was going to be a tough night for me. I thought he played great. I played great in some moments. Overall a win is a win. It was a very emotional win and a tough win knowing the significance of tonight’s match. After a really terrible second-set tie-break I think I played a really solid third set.”
Earlier, Jannik Sinner delighted the crowd in Turin by defeating Stefanos Tsitsipas in the opening singles match.
The 22-year-old Italian played as an alternate two years ago but qualified for the first time this season after claiming four ATP Tour titles and rising to world No 4. He is one of the favourites to lift the trophy this week, which would be the dream scenario for the home fans, and a 6-4, 6-4 victory over Tsitsipas is a big step towards the semi-finals.
There had been doubts over Tsitsipas’s fitness heading into the event and he failed to force a break point on the Sinner serve during the 85-minute contest.
“I was excited to step on court and opening the finals is really, really special,” said Sinner. “I knew it was going to be very tough but I think I handled the situation well. I tried to stay aggressive and I am very happy with the performance. I am happy to start off with a win and hopefully I can continue with this intensity.”