Imola marks Senna's death
Ayrton Senna pours champagne over himself to celebrate his victory in the Brazilian Grand Prix, Sao Paulo, on March 28, 1993 - by Julio Pereira
A memorial service is being held at the Tamburello corner where the triple world champion's Williams careered off into a concrete barrier on lap seven at 190mph (307km/h).
He was airlifted to Bologna hospital but was pronounced dead at 18:40 local time on that ill-fated Sunday.
Thursday's ceremony comes after a week of commemorative events held to mark the tragic accident that claimed the life of the driver regarded by many as the greatest of all time and which ushered in a raft of changes to improve F1 safety.
The Senna anniversary is made all the more poignant as another great F1 driver, seven-time champion Michael Schumacher, continues his fight for life after the German's skiing accident on December 29.
Ironically, it was Schumacher who went on to win the Imola race 20 years ago.
Senna's death, 24 hours after Austrian rookie Roland Ratzenberger was killed and two days after his fellow Brazilian Rubens Barrichello was injured, was the sport's blackest weekend.
And all this week emotional tributes have been paid to the 1988, 1990 and 1991 champion.
"He was an incredible legend," said 2008 champion Lewis Hamilton.
"You like to think that one day you may be recognised as someone that was able to drive similarly to him," added the Mercedes driver.
"On my schoolbooks I didn't have pictures of girls, obviously I was too young but I had Ayrton there and the same in my room," said 2005/06 champion Fernando Alonso.
Senna's sister Viviane, told AFP this week that her brother's legacy is alive and well through the Ayrton Senna Institute which she chairs.
She recalls a conversation she had with him weeks before his death when he told her how he wanted to contribute to a better future for Brazil by helping to open up opportunities for children.
She said: "Ayrton really wanted Brazil to work, for everyone to have a chance and from this dream the Institute was born.
"Currently, we are working with more than two million children and training some 75,000 teachers per year across around 1,000 cities around the country."
Senna's death prompted extensive changes, including the reform of the Grand Prix Drivers' Association. Engine capacities were reduced and tethers to help prevent wheels flying off following accidents were introduced.
The HANS device to protect drivers' heads and necks were made compulsory, and run-offs were extended and improved.
As evidence that the improvements put in place worked the last F1 fatality in a grand prix was Senna.
Imola is opening its door to F1 fans from Thursday through Sunday when as well as the Tamburello corner ceremony there will be a parade, a presentation on current F1 security and a F1 drivers' charity football match.