Emergency Services were called to the Bunbury Museum and Heritage Centre, about 175km south of Perth, about 10.30am local time (1.30pm AEDT) yesterday.
St John Ambulance paramedics treated the child at the scene and he was rushed to hospital.
He was later flown to Perth Children’s Hospital where he remains in a critical condition.
St John WA confirmed the child suffered “critical injuries” and the incident was treated as “priority 1”.
It’s understood the boy was hit by a parking meter in a courtyard of the museum.
The museum has been closed for the remainder of today and tomorrow following the incident.
“We apologise for any inconvenience and thank our community for their patience and understanding during this period,” Bunbury Museum and Heritage Centre said on Facebook.
WA Liberal leader Libby Mettam yesterday described the incident as a “tragic accident”.
“Our hearts go out to the boy involved and his family, and we hope for a speedy recovery,” Mettam told media.
City of Bunbury chief executive Alan Ferris said he was saddened to hear the child had been injured.
“We thank police and paramedics who not only helped the child, but museum staff and community members who witnessed the incident and provided immediate assistance,” he told ABC.
“Our thoughts are with the child, their family, and all involved and everyone impacted.”
WorkSafe WA has been contacted for comment.