The flag of the former county of Østfold, Norway. Its design is shared with the county arms, and shows a sunbeam, which makes two different links symbolically. Firstly, as the sun rises in the east, it refers to the name and geographic location of the county ("øst" means east in Norwegian). Secondly, the solar design alludes to the fertility worship expressed in the numerous Bronze Age petroglyphs found in Østfold. In heraldry, the rays of the sun are often depicted as alternatingly straight and wavy, with the straight rays being said to represent light, and the wavy ones heat. The flag was approved by royal resolution 1958‐09‐26.
Østfold fylke, flagg – Arkivverkets digitale fotoarkivForskrift om fylkesvåpen og fylkesflagg, Østfold – Lovdata
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(Sources of the oldest file version:)

Based on File:..Østfold Flag(NORWAY).png and File:Østfold våpen.svg
Hallvard Trætteberg, vectorization by VulpesVulpes42
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(Authorship information for the oldest file version:)

PNG flag by AlexR.L. (CC-BY-SA 3.0)Coat of arms by SKvalen (PD-Norwegian CoA)SVG flag by SiBr4