"The website will share information on high-profile internationally-wanted criminals, convicted of - or suspected of having committed - serious crimes or terrorist acts in Europe," Europol said.
"This is the first initiative on a pan-European level to jointly present a most wanted list on a common platform," the European police agency added in a statement.
People are encouraged to provide tip-offs - anonymously if they want - at www.Eumostwanted.Com.
The site's launch comes after sharp criticism of the coordination between European authorities in the wake of the Paris attacks.
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Europol said the website aimed "at increasing security" across the European Union by having the public "help police trace Europe's most wanted fugitives".
Each of the 28 EU members will select a number of key fugitives for the list, which will be regularly updated, the agency added.
A picture of each of the suspects is prominently displayed, along with a description of the allegations against them and a phone number of the police force hunting for them.
He is described as a "very dangerous, armed individual."
A total of 130 people died in the November 13 attacks on the French capital and an international manhunt is underway for Abdeslam.
One woman, Maria Cecilia Kettunen, 29, from Finland is on the list, accused of "aggravated fraud of significant amount of money" without further details.
Another fugitive is Ernesto Fazzalari, 45, wanted by the Italian police as a "key figure of a mafia clan dubbed Avignone-Zagari-Viola" which is "at war with another clan".
Some of the unresolved crimes stretch back years. Romanian "yoga teacher and spiritual mentor" Gregorian Bivolaru, 63, is wanted for exploiting children and child pornography between 2002 and 2004.
Available in 17 languages, the website was launched by ENFAST1, a Europe-wide police network specialised in hunting down and arresting fugitives with Europol's help.