FTSE 100 firm is currently made up of a wealth management arm, an international asset management business, an emerging markets division, and a majority stake in South African lender Nedbank.
But chief executive Bruce Hemphill, who joined the group in November, said that after completing a strategic review of the group, separating its units would unlock further value.
The firm plans to split into Old Mutual Emerging Markets, Old Mutual Wealth, Nedbank Group and OM Asset Management.
Its target is to complete the moves by the end of 2018.
Hemphill said: "The strategy we have announced today sets out a bold new course to unlock value currently trapped within the group structure.
"We have four strong businesses that can reach their full potential by freeing them from the costs and constraints of the group.
The group has a 54.1% holding in South African lender Nedbank, but said over time it will reduce this to "an appropriate strategic minority position".
However, it intends to maintain close links with Nedbank as "their commercial relationship continues to be a source of value underpinning successful collaboration activities in both South Africa and the rest of Africa".
Old Mutual said it does not intend to sell its stake in Nedbank to "a new strategic investor", and wants shares in the bank to be widely held.
Old Mutual also presented its annual results, which showed that pre-tax adjusted operating profit rose 4% to £1.7bn in the year to the end of December compared to a year ago.
The group, which was founded in South Africa in 1845, has turned its attentions to expanding in Africa in recent years. It has more than 17.5 million customers, holds £304bn of funds under management and employs more than 61,500 staff.
Helal Miah, investment research analyst at the Share Centre, said: "While we are supportive of Old Mutual's plans to strengthen its business, a low-growth environment and global volatility remains a challenge."
Shares fell 3% in early trading.
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