The anniversary comes with America digesting the report from the Department of Justice detailing racial bias in Ferguson, a city which saw violent protests over the killing of an unarmed black man by a white police officer last summer.
Barack will deliver a speech to commemorate the marches that took place to protest against the lack of voting rights.
On that day in 1965, 600 peaceful activists were attacked by police with clubs and tear gas.
A unity march of leaders from all faiths will be staged over the weekend.
Dr Jerry Light, leader of the First Baptist Church, said: "1965 was a horrible time for Selma but it was a horrible time for all of the South and, just like many of the other cities, we have overcome.
"We are not where we want to be but we are working in that direction."
Mr Obama will later be joined in Selma by the first family and former president George W Bush.
