Silversea chairman Manfredi Lefebvre D’Ovidio said the agreement would bring together two lines with “bold, long-term visions for the cruise industry”.
Richard Fain, chairman and chief executive of Royal Caribbean, said: "Silversea is a crown jewel, and the acknowledged leader in luxury and expedition cruising, two key markets that are poised for growth.
"Uniting our two companies presents an extraordinary opportunity to expand vacation options for guests and create revenue in strategic growth areas."
Under the agreement, Royal Caribbean will acquire a 66.7% equity stake in Silversea based on an enterprise value of approximately $2 billion.
The purchase price of the equity being acquired is approximately $1 billion.
RCCL plans to finance the purchase through debt.
As part of the deal, Lefebvre D’Ovidio will remain executive chairman of Silversea and continue to lead its strategy long term.
In addition, he will qualify for an estimated contingent consideration of approximately 472,000 RCCL shares, payable upon achievement of certain 2019-2020 performance metrics.
Lefebvre D’Ovidio and Fain confirmed that Silversea chief executive, Roberto Martinoli, will continue in his role, working with the existing Silversea management team.
The deal is expected to be completed later in the year, subject to customary closing conditions and regulatory approvals.
Outlining the strategic rationales for the agreement, the lines said it would help drive long-term capacity growth in the luxury and expedition markets “at a much larger scale than what Silversea would achieve independently”.
RCCL added the acquisition would also help to diverse its portfolio surrounding expedition by adding “a premiere ultra-luxury brand”.
Fain said the RCCL was “proud” to welcome Lefebvre D’Ovidio to the group, calling him “a visionary leader whose high standards and history of innovation we deeply respect”.
Lefebvre D’Ovidio added: "This partnership will bolster the growth of this exceptional brand founded by my father.
"I have always been kindred spirits with Richard and we share a vision of offering excellence and leadership to our guests. This new partnership gives Silversea the opportunity to accelerate the growth of the most successful luxury and expedition cruising brand in the world."