Police put a rolling roadblock in place at around midday as they struggled to get the animal in order.
It happened eastbound on Saturday between junction 3-4 at around midday.
Ryan Thompson tweeted: ‘Traffic slow on M27. Loose horse now been caught safe and well.’
He told The News: ‘(It was) Saturday on M27 from junction 1 all the way to Rownhams Services.
‘It had a full saddle and stirrups, and ran for about six miles until it was knackered then stopped. Police led it into Rownhams.’
Romanse, a traffic monitoring service, said: ‘#M27 eastbound - rolling road block at #Rownhams Services whilst a horse is moved from the carriageway, delays back past J2/#A36 #Ower.’
At around 12.20pm Romanse tweeted: ‘#M27 eastbound - rolling road block now CLEARED at #Rownhams Services after a horse was moved off the carriageway, delays remain back past J2/#A36 #Ower.’