Police described the event on Salisbury Plain in Wiltshire as one of the safest in years, although 34 people were arrested for minor drug offences.
Sunrise, marking the longest day of the year north of the equator, occurred over the circle at 0452 BST.
The Heel Stone, just outside the main circle, aligns with the rising sun.
Peter Carson from English Heritage said: “It has been quieter this year but it’s been a great solstice.
“It’s an improvement on the last few years – the last time I remember seeing the sun rise was in 2003 – so it’s great to see the sun has put in an appearance.
“This year there are about 20,000 people and last year it was about 35,000 – so that is quite a bit down which has meant the operation is a lot easier. ”
He said two years ago the solstice happened early on a Saturday and about 30,000 people attended.
He added: “I think the days of the week do make a considerable difference to the number of people who come along – this year it’s a Monday morning.
“The people who are streaming out now – a lot of them are going to work.”
Victoria Campbell, 29, was among those marking the solstice.
She said: “It means a lot to us…being British and following our pagan roots.”
The Londoner, who works in the finance industry, added “getting away from the city” was a major draw.
On Sunday police chiefs said they had planned for “all eventualities” ahead of the event.
Last year a record 36,500 revellers attended, causing traffic chaos and road closures.
Merlin @ Stonehenge