The Juventus defender becomes just the seventh player to reach the milestone, following in the footsteps of Andrea Pirlo, Gianluigi Buffon, Paolo Maldini, Dino Zoff, Daniele De Rossi and Fabio Cannavaro.
Chiellini reaches his century exactly 14 years after he made his international debut as a second half substitute in a 1-0 friendly victory against Finland.
It is a feat that seemed impossible just 12 months ago, when Chiellini announced his international retirement in the wake of Italy’s shock failure to qualify for the World Cup.
The 34-year-old said he wanted to step aside in order to allow the team to begin a ‘new era’ following their play-off defeat against Sweden.
However, just four months later Chiellini was included in the Italy squad by interim boss Luigi Di Biagio for friendlies against Argentina and England, though injury would ultimately force him to withdraw.
New permanent head coach Roberto Mancini also called-up Chiellini to his squad and even appointed him captain following the retirement of Gianluigi Buffon.
Despite his advancing years, Chiellini has continued to play a key role in a Juventus side that has dominated Serie A over the past few years.
He is Juve's seventh-longest serving player of all time, having racked up close to 500 appearances since signing from Roma in 2005.
During his time in Turin he was won seven successive Serie A titles as well as winning the Coppa Italia four times and the Supercoppa Italiana on three occasions.
The defender signed a new contract in the summer extending his stay at the club until 2020. He also succeeded Buffon as Juventus captain following the veteran goalkeeper’s departure to Paris Saint-Germain.
Chiellini couldn't mark the occasion with a win however, with Portugal holding on for a goalless draw in Milan.
The result means Portugal win Group A3 and progress to next summer's Nations League finals, with Italy having to settle for second spot.