The former Netherlands boss has been axed after his side's latest 4-2 defeat at Eintracht Braunschweig, which leaves them embroiled in a relegation battle
The loss was Hamburg's seventh consecutive league defeat in a row, form which sees the seven-time German champions in 19th and embroiled in an unlikely relegation battle.
"We looked at our situation and were forced to make this decision which we regret. We thank van Marwijk for his efforts," club sporting director Oliver Kreuzer told reporters.
"This was disappointing," van Marwijk had said after the loss at Eintracht-Stadion. "Two teams fighting relegation were playing each other, something we were not used to.
"There are no resilient characters in this team, something we need most at this time. My players are in a lurch. This is the hardest job of my career."
Wednesday's 5-0 loss to Bayern Munich in the DFB-Pokal compounded matters for the former Netherlands boss, who lasted only 143 days in the job after taking over from predecessor Thorsten Fink last September.
Former Hannover 96 trainer Mirko Slomka has been linked with the dugout, while club favourite Martin Jol is also tipped for a return.
Felix Magath had put himself forward before joining Fulham, although he revealed that the club's board had turned him down.