A semi-finalist four times here, Henman has never reached the final. Once more he remains Britain's last hope of a home men's singles champion in 68 years and Philippoussis had presented a major obstacle.
Henman, however, was unfazed, producing masterful tennis the first two sets before finally squeezing home 6-2, 7-5, 6-7, 7-6.
"Tough to make sense of it now, it was such an intense match," Henman said. "He had to stick in there because I got off to a great start. Third set was tough, I didn't lose my serve but he played the better tiebreak.
"I had to stay mentally strong and managed to finish it off."
Henman, who faces Croatia's Mario Ancic next, was joined in the quarters by Roger Federer after the Swiss champion felled the tallest man in tennis.
TOUGH MATCHES
The top seed held his serve throughout to remain unbroken all tournament and beat 6ft 10ins (2.083 metre) Ivo Karlovic 6-3, 7-6, 7-6.
"I have faced that pace before but his serve comes down at you from such an angle," Federer smiled. "It's a different challenge.
"But back in the quarter-finals here again. It was a really tough match today ... big satisfaction."
Federer will meet 2002 champion Lleyton Hewitt in the quarters. Beaten by Karlovic in the first round last year, the Australian out-hit fellow former world number one Carlos Moya in a thriller on Centre Court.
Hewitt triumphed 6-4, 6-2, 4-6, 7-6 to set up the mouth-watering last eight clash with his successor as champion here.
"I knew I was in for a tough match even though grass isn't his surface and I am just delighted to win," Hewitt said.
Looking forward to facing Federer, he added: "He is the form player here, the defending champion ... I am looking forward to the challenge but I have to up my game.
"I've had some tough matches with him in the past and I don't expect anything different."
Second seed Andy Roddick silenced the booming serve of Alexander Popp 7-5, 6-4, 6-4 to take his place in the Wimbledon quarter-finals and faces Sjeng Schalken next.
The other quarter-final will feature France's Sebastien Grosjean and German Florian Mayer.
In the women's draw, Maria Sharapova and Karolina Sprem led the new guard into the quarter-finals, both negotiating their way past more experienced opposition.
Steely Siberian Sharapova has barely put a foot wrong all grasscourt season and on court one she put paid to Amy Frazier's hopes 6-4, 7-5.
CARRIED FLAG
Aged just 17, the Russian reached the quarter-finals of the French Open last month and signalled that she is a dangerous prospect on all surfaces by winning the Edgbaston event on grass in the run-up to Wimbledon.
On Monday she beat her 31-year-old opponent in every department to book a last-eight clash against Japan's Ai Sugiyama who beat Thai Tamarine Tanasugarn 6-3, 7-5.
"She made me work for it until the last point," the Russian said of Frazier. "I was very relieved, she is in great form ... I had to fight through it, what can I say?"
Sprem, conqueror of Venus Williams in the second round, continued her winning ways with a 6-4, 6-4 win over 21st seed Maggie Maleeva.
The 19-year-old Croatian, who claimed the scalp of 32nd seed Meghann Shaughnessy in the last round, is in the last eight of a grand slam for the first time.
"Great, perfect, unbelievable feeling," the teenager smiled. "I'm tired right now. It's good that I have tomorrow off."
Sprem faces a huge challenge next. She plays former champion and fifth seed Lindsay Davenport for a place in the semis.
Davenport carried the flag for the twenty-somethings, beating Russian 12th seed Vera Zvonareva 6-4, 6-4.
The 1999 champion, who has yet to lose a set in this year's tournament, is looking increasingly dangerous in a wide open bottom half of the draw.
"I'm just concentrating on the job in hand," the American said.
In the top half of the draw, Tatiana Golovin and Silvia Farina-Elia both won their third round matches held over from Sunday because of rain.
