Bjärka-Säby gamla slott, 17th-century castle in Linköping, Sweden.

Bjärka-Säby gamla slott stands on the northeastern shore of Lake Stora Rängen. Its main building is a three-storey grey-stone house with a gabled roof, its main portal dated 1632. Two single-storey timber wings with säteri roofs were added in front in the early 18th century; the southeast wing is still used as a residence.

Bo Jonsson Grip acquired Bjärka in 1367 and built the fortress Bjärkaholm on an islet in the Stångån; by 1370 it was ready, and he bought neighbouring Säby the next year. Around 1630 Per Nilsson Natt och Dag began a stone manor whose main portal bears the date 1632 and the arms of him and his wife Sofia Stenbock; after his death two years later she finished it. In the late 17th century Germund Cederhielm took over the estate and added two wooden baroque wings.

The name Bjärka-Säby combines the old Bjärka estate with neighbouring Säby, bought by Bo Jonsson Grip in 1371. The southeastern wooden wing, fitted out as a residence by Germund Cederhielm, is still lived in today. The old stone house later served as a guest house, and the whole castle can now be rented for weddings and celebrations.

The old castle stands on the northeastern shore of Stora Rängen, about 20 km southeast of Linköping and 4 km north of Bestorp. The main building and its two wings can be rented for celebrations such as weddings, and the southeastern wing is still lived in, so visitors should keep to the courtyard and exterior.

The main portal bears the year 1632 and the coats of arms of builder Per Nilsson Natt och Dag and his wife Sofia Stenbock. The Natt och Dag family held Bjärka and Säby for six generations, from 1386 until Carl Persson had to hand the estate to Germund Cederhielm at the end of the 1600s.