Del Rosario, who served under Philippine president Benigno Aquino from 2011 to 2016, died while en route to the United States, the Department of Foreign Affairs (DFA) said in a statement that did not specify the cause of death.
Born in Manila in 1939, he went on to graduate with a degree in economics from New York University and later became a fierce critic of China.
Del Rosario was "a staunch advocate of protecting and advancing national security and promoting the rights and welfare of Filipinos", the foreign ministry said.
"He was a consummate diplomat and an inspiring leader who led the DFA with integrity and unwavering commitment to public service," Foreign Affairs Secretary Enrique Manalo tweeted.
Relations with Beijing soured during his tenure, which was marked by a fierce standoff in 2012 in Scarborough Shoal, a chain of reefs and rocks 240 kilometres (150 miles) west of the main Philippine island of Luzon.
He was behind two prominent legal cases against Beijing, including a 2013 case at an international tribunal that eventually struck down China's claims to most of the resource-rich South China Sea waterway.
Del Rosario continued his criticism of China after leaving office by holding public forums organised by his think tank and writing opinion columns in local newspapers.
In March 2019, del Rosario filed a complaint against Chinese officials at the International Criminal Court, alleging "crimes against humanity" over the supposed environmental fallout of Beijing's activities in the South China Sea.
The complaint was eventually dismissed because China is not a state party to the Rome Statute that established the court.
Months after filing the ICC case, he was denied entry to Hong Kong in what critics called retaliation for his criticism of Beijing.
Related Links
Learn about the Superpowers of the 21st Century at SpaceWar.com
Learn about nuclear weapons doctrine and defense at SpaceWar.com
| Subscribe Free To Our Daily Newsletters |
| Subscribe Free To Our Daily Newsletters |
