On Tuesday, city deacon Johannes zu Eltz showed the press the empty shrine, which is set into a wall in a side chapel next to the main altar.
The gold-plated monstrance (relic container) and the remains of Saint Hedwig, a baroness of Silesia in the early 13 Century, had been on display there on a permanent loan from the city of Görlitz since the autumn.
Hedwig is revered as a patron in Germany and Poland and is considered a comforter for those who have been driven from their homelands.
The centre piece of the shrine was a small capsule which contained shards of the holy woman's skull.
Zu Eltz noticed the theft on Monday and described how it had unsettled him.
“The relics had a huge sentimental value for believers,” he told the Frankfurter Allgemeine Zeitung.
The shrine which contained the relic. Photo: DPA
The lock which secured the metal bars in front of the 25-centimetre compartment was missing when the theft was discovered.
The key was still in its original place in the vestry, leading to the suspicion that the thief cut through the lock with a bolt cutter.
“Maybe it was just some idiot who wanted to make a quick buck,” zu Eltz commented.
If that was the case, the thief is likely to be disappointed. Police estimate the value of the gold-plated monstrance at a few thousand euros.
“Melting it down wouldn't be worth the hassle,” the deacon said, adding that the relic would be hard to sell.
The cathedral is offering a “generous finder's fee” to anyone who can provide information which leads to its discovery.
This is the first theft from the cathedral during his time in office, zu Eltz said, but he added that it would not change the fact that the church remains open to everyone during the day.
“The cathedral in no high security area, it must remain a place of freedom,” he insisted.