UN Secretary-General Antonio Guterres sent a letter to the Security Council on Tuesday announcing his intention to appoint Pedersen, 63, currently Norway's ambassador to China.
A seasoned diplomat, Pedersen was a member of the Norwegian team to the secret negotiations that led to the signing of the 1993 Oslo accords between Israel and the Palestinians.
He will succeed Italian-Swedish diplomat Staffan de Mistura, who announced he was stepping down to spend more time with his family after four years in the demanding post.
De Mistura was appointed in July 2014 after veteran Algerian diplomat Lakhdar Brahimi resigned following two years in the position.
Brahimi stepped in after former UN chief Kofi Annan quit just six months into the role. Annan described the Syria envoy's job as "mission impossible".
UN spokesman Farhan Haq announced the appointment and said Pedersen is expected to begin work at the end of November.
Pedersen will take over at a time when Syrian government forces have made major territorial gains in the seven-year war, with the military backing of Russia and Iran.
UN diplomatic efforts to end the war have stalled but the world body leads a massive humanitarian effort to help millions uprooted and in need of medical and food aid.
More than 360,000 people have been killed in the war, which began in March 2011 as an uprising against President Bashar al-Assad but has morphed into a complex conflict with myriad armed groups, many of whom are foreign-backed.
Reporting on his latest efforts, De Mistura told the council last week that the Syrian government had rejected a UN list of members to a proposed committee tasked with drawing up a post-war constitution for Syria.
The committee is to be comprised of three groups of members, one proposed by the Syrian government, the second presented by the opposition and the third by the United Nations to include civil society representatives, religious leaders and others.
Last year, Russia, Iran and Turkey set up the Astana process to advance diplomatic efforts in Syria, a move that effectively sidelined the UN-led peace process that De Mistura was shepherding in Geneva.
Norwegian Foreign Minister Ine Eriksen Soreide welcomed Guterres' decision to appoint one of her country's "foremost diplomats" and stressed that "finding a political solution to the conflict in Syria is one of the most difficult tasks facing the UN".
Pedersen has some knowledge of Arabic and is considered a skilled negotiator who can "find solutions and compromises in difficult issues", a Norwegian diplomat said.
The father of five served as Norway's UN ambassador from 2012 to 2017 before becoming his country's envoy to China last year.
He was special coordinator for Lebanon from 2007 to 2008 and UN envoy for southern Lebanon from 2005 to 2007. He also worked as director of the Asia and Pacific division in the UN political affairs department.
Pedersen also served as Norwegian representative to the Palestinian Authority between 1998 and 2003.