The international NGO said on its website that World Toilet Day provides an opportunity to "remind others of the importance of better sanitation for everyone."
World Toilet Day was first declared in 2001, when world sanitation experts from 200 countries set up the Singapore-based World Toilet Organization.
The event "is now being celebrated by members all over the world," the website said.
"Each year lack of toilets causes 200 million tons of human waste to go uncollected and untreated around the world, fouling the environment and exposing millions of people to diseases," the group said.
According the World Health Organization, 2.5 billion people have no access to a hygienic toilet, over half of which live in China and India. The United Nations has set a goal to halve this figure by 2015.