Research by the charity found that more than 100 million people on earth are forced to practise what's known as 'open defecation' - using roadsides, railway tracks, or plastic bags as a toilet.
Here are the top 10 countries with the most urban dwellers without safe, private toilets:
India has the highest number of urban dwellers who do not have access to safe and private toilets - 157 million people.
Eight Olympic-sized swimming pools could be filled daily with excrement produced by India's 41 million urban residents who must defecate in the open.
China, which also has a massive rate of rural to urban migration, is the second worst, with 104 million people without safe sanitation.
However, WaterAid also ranks China top of the “most improved” countries for reaching the highest number of people in urban areas with safe, private toilets. The state has managed to build sanitation facilities faster than the pace of new arrivals, providing more than 329 million people since 2000 with urban sanitation systems, outpacing population growth by 9 million
A newly launched report on the 2016 State of the World Toilet by WaterAid Nigeria has revealed that 130million representing 71 percent of Nigerians lack access to safe, private toilet. 58 million people out of the number living in urban cities lack access to improved sanitation facilities and 13.5million urban dwellers defecate in the open, the report further noted.
Other countries that make the top 10 list are:
7. The Democratic Republic of Congo
According to research, every $1 spent on sanitation and water generates a $4.3 return in the form of reduced health care costs.
(credits: Thomson Reuters Foundation, the charitable arm of Thomson Reuters, that covers humanitarian news, women's rights, trafficking, property rights and climate change.)
World Toilet Day is an important reminder that plumbing and sanitation are a blessing to many. Diarrhea resulting from poor sanitation such as inadequate toilets and dirty water kills 315,000 children yearly, according to estimates by WASHwatch, an online project that collects data on water and sanitation.