The UN aims to raise up to 1.4 billion euros ($1.5 billion) in commitments throughout 2017 for the Lake Chad region, which comprises northeast Nigeria, northern Cameroon, western Chad and southeast Niger.
One of the poorest regions in the world, it has been ravaged by eight years of violence. Schools, dispensaries and agriculture are in ruins, and people have been forced to flee jihadists on foot without any resources.
Across northeast Nigeria, some 5.1 million people face severe food shortages and nearly 500,000 children are suffering from acute malnutrition, even as the military makes gains against the group.
Norwegian Foreign Minister Borge Brende, meeting with non-governmental organisations on Thursday, called it "one of the more forgotten conflicts" on the planet.
"The displacement crisis in northeastern Nigeria and the Lake Chad region has really become unfortunately a very serious food and nutrition emergency," Brende said.
"More than 10 million people are in need of assistance... Some parts of northeastern Nigeria may unfortunately already experience famine," he added.
The medical situation has been described by Doctors Without Borders (MSF) as "the worst in the world".
Humanitarian organisations can access populations at risk only as the army progresses. Many roads are only passable under the escort of Nigerian soldiers and ambushes are a constant threat. Other places are only accessible by helicopter, where "horrible rates of malnutrition" are observed among children.
"In the whole of the Lake Chad region we've seen the fight against Boko Haram take priority above all else, with military and political objectives directed towards this," said Natalie Roberts, head of emergencies for MSF in Borno state.
"We now find ourselves in the midst of a huge humanitarian crisis," she added.
The UN humanitarian coordinator for the Sahel region, Toby Lanzer, called for a response to "one of the most deadly extremist groups," referring to Boko Haram.
The inhabitants "are surviving with barely one meal a day," he warned. "And we know that with the impending rainy season, disease will increase, malaria will become more prevalent, and shelter will be more needed," Lanzer said.
Ahmed Shehu, a civil society representative in northeastern Nigeria, spoke about the need for long-term development.
"I say (to) donors here, if we want to tackle the Boko Haram issue, let's also reflect on the underlying issue: poverty," he said.
"The second issue we fail to link with Boko Haram is climate change," he said, noting that 90 percent of Lake Chad has dried up in a few decades. "What is the issue now? A majority (farmers and fishermen) have lost their livelihoods," he said.
Among those attending the Oslo conference are government ministers from Germany, Norway, Nigeria, Niger, Chad and Cameroon, as well as the UN High Commissioner for Refugees Filippo Grandi and the head of the World Food Programme, Ertharin Cousin.
On Friday, delegations are expected to detail their respective commitments in three-minute speeches.