The safari park near Warminster was home to female hippos Sonia and Spot for nearly 50 years.
Since their deaths in 2023 and January respectively, visitors have been wanting the breed to return.
Now, the park plans to introduce a group with a bull and females, with enough space for any offspring, creating a self-sustaining family group known as a bloat.
In plans submitted on November 15, it has asked Wiltshire County Council for permission to build a new hippo house on the existing structure’s site.
It has also asked for permission to improve the grazing paddock and Half Mile Pond.
The new structure will also feature indoor pools for the hippos and a classroom for educational talks, tours, and group visits.
Simon Askew, interim chief operating officer, said: “We want to be part of the European Breeding Programme for this iconic species.
“Our hippos were much-loved by visitors and staff alike and we want to enable their return as part of our commitments to conservation and education of this incredible species.
“Hippos were first introduced to Longleat in 1967, just a year after the safari park first opened.
“Sonia and Spot were the most recent and could be seen living peacefully alongside other animals that reside in and alongside Half Mile Pond including sea lions, gorillas, and colobus monkeys.
“Plus, more recently, native beavers who made the area their home.”
Mr Askew said if the hippos are brought back to Longleat, they would have access to the largest free-range water habitat for hippos in the UK, as well as seven acres of grazing land.
He continued: “Advances in hippo care means we want to invest in the modernisation of the housing available.
“Continuing the story of hippos at Longleat would enable us to play an invaluable role in raising public awareness about conservation issues.”
Mr Askew said Longleat has the potential to become a key part of the European breeding programme for the species.
He added: “This plan uses the space we have to house one of the largest groups of hippos in Europe and be a UK and international leader in the care and conservation of hippos.
“This is significant investment for conservation and for Longleat.”
If planning permission is granted, Longleat aims to bring hippos back to the estate in summer 2025.