The south coast club went down without kicking a ball on the day, any flickering hopes of survival finally snuffed out by West Ham United beating Sunderland 1-0.
In truth, their chances had already been effectively killed off when they were docked nine points for going into administration in February.
With West Ham moving four points clear of the drop zone, Portsmouth are mathematically unable to escape with five matches remaining. The result ended Pompey's seven-season stint in the top flight.
Brazilian striker Ilan sealed Portsmouth's fate with a 51st minute strike, his second goal in as many games bringing a smile to the face of manager Gianfranco Zola.
"I am really delighted for the players and everybody involved with West Ham," he told Sky television. "We've gone through a difficult time. It's still not easy, but a little bit better."
Put up for sale by Alexandre "Sacha" Gaydamak last August, United Arab Emirates businessman Sulaiman al-Fahim stepped in before selling on to Saudi Ali al Faraj.
Hong Kong businessman Balram Chainrai became the fourth owner in less than a year, saying he had "zero interest" in running the club and hoped to offload it as soon as possible.
Gaydamak's father Arkady, a Russian-Israeli businessman, was convicted by a French court last year of illegal arms deals, tax fraud, money laundering, embezzlement and other crimes.
"The adverse publicity surrounding Sacha's father sent the banks who provided us with overdraft facilities into meltdown," former chief executive Peter Storrie said in February.
"Overnight we had to find nearly 50 million pounds as well as sustain the running of the club."
