Mobiloo toilets are designed for people unable to use a toilet independently on their own.
Anna Bird from Mums on a Mission talked about the importance of the toilet, which will be at Lydiard Park on 24 July from 10am to 4pm.
She said: “Swindon has some beautiful open spaces and our children love being outdoors as much as any other child. But our visits to places like Lydiard and Coate Water are normally cut short, because we cannot meet our children’s toileting needs.
"Our hope is that Swindon Borough Council see that the mobiloo is well used, and will look to install some permanent facilities for families like us to use in our parks in future."