To increase safety, many zoos are implementing measures such as hand sanitising, one-way systems and social distancing in line with government guidelines.
Indoor areas of the parks will have to remain closed until guidance allows says it is safe to do so.
The Zoological Society of London, which owns and runs ZSL London and Whipsnade Zoo in Bedfordshire, says its zoos must be pre-booked by customers.
They said: “Both ZSL London and Whipsnade Zoos are safely open again from Monday 12 April onwards.
“We’re delighted to welcome you back through our doors to our safe outdoor spaces to see our incredible animals.”
On the morning of the opening, the rhinos at Whipsnade Zoo put on a “smashing opening ceremony” as staff had stacked boxes in their paddock that read “We are open”.
In a video posted on Twitter, the rhinos knocked over the boxes and played with them, nudging them with their horns.
Following the death of Prince Philip on 9 April, the ZSL London Zoo posted a tribute to the Duke of Edinburgh, who has “supported” it for years.
It said: “HRH, The Duke of Edinburgh had a lifelong passion for wildlife.
“He supported ZSL for many years. Here, in 2013, he opens Tiger Territory, as Sumatran tiger Jae Jae looks on.
“We are so grateful to HRH Prince Philip and the Royal Family, who remain in our thoughts at this sad time.”