Porsche 901 was the name originally intended for the Porsche 911.
By the early 1960s, Porsche project design numbers had reached into the 800s. For instance, Porsche's 1962 F1 model was called Porsche 804.
At the Internationale Automobil-Ausstellung (Frankfurt Motor Show) in Frankfurt in September 1963, Porsche presented its successor to the Porsche 356 as the 901. It took several more months until the cars were manufactured for sale to customers. Between 14 September and 16 November 1964, 82 cars were built and the 901 was presented in October at the 1964 Paris Auto Salon. There, French car maker Peugeot objected to Porsche using any three digit number where the middle number was 0, asserting ownership of the naming rights in key markets, and having already sold many models with that scheme.
So, Porsche simply replaced the middle 0 with a 1, and called the car Porsche 911. Officially the 901s already constructed were used for testing and for exhibitions, and Porsche sold none to private customers. Nevertheless, several of the cars retained by Porsche at that time appear to have made it to private ownership subsequently: in 2010 it was reported that car number 37 was owned by a Porsche specialist named Alois Ruf.