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The histories of orogenic eclogites in the high-pressure Bohemian Massif, Czech Republic are debated. Oxygen isotope ratios help determine if they crystallized in the mantle, or within oceanic or continental crust. Using 55 new laser fluorination values and 9 published δ 18 O values of garnet from eclogites, host gneisses, and ultramafic rocks from the Bohemian Massif, comparisons were made to δ 18 O (Grt) from 1055 new and published values from other eclogites, HP mafic rocks, and oceanic crust to attempt to distinguish protolith. Of all Bohemian eclogite samples, 40% fall in the normal range for high-T equilibrium with typical mantle (δ 18 O (Grt)= 5.3±0.6‰); 37% are< 4.7‰, and 23% are> 5.9‰. Eclogites found in gneiss (external eclogites) from the Bohemian Massif range in δ 18 O (Grt) from 1.4‰ to 7‰ indicating that eclogite protoliths interacted with heated meteoric water or seawater before garnet growth. External eclogites are not equilibrated with their host gneisses at meter-scale. No negative δ 18 O (Grt) values were found and the range of δ 18 O values of external eclogites are similar to that of δ 18 O (WR) of hydrothermally altered oceanic crust and to δ 18 O (Grt) of oceanic crust-derived Alpine eclogites. Exchange with heated meteoric water in a continental setting cannot be ruled out by the new δ 18 O (Grt) data, but would imply fortuitously low water/rock ratios for all samples studied. Tectonic models exist that allow for both the subduction of continental crust to HP and the interlayering of oceanic crust with continental crust. Eclogites associated with ultramafic rocks (internal eclogites), have a smaller range in δ 18 O (Gt) from 3.1 to …