A four-funnel liner, also known as a four-stacker is an ocean liner with four funnels. Kaiser Wilhelm der Grosse, launched in 1897, was the first ocean liner to have four funnels and was one of the first of the golden era of ocean liners that became prominent in the 20th century. Mauretania was the fastest of all four-funnelled liners. The last four-funnelled liner ever built was Windsor Castle; however, two of her funnels were later removed making the Aquitania the last four-funnel liner in service and the only one to survive service during both World Wars.