Abstract Discoveries of gamma-ray bursts (GRBs) have become commonplace in recent decades, totalling O (10⁴) unique detections across various missions. However, there have been no confirmed discoveries of a gravitationally-lensed GRB, despite expected lensing rates of ∼1 in 103. In light of this, we complete an archival search for lensed GRBs by cross-matching well-localised Swift/XRT-detected bursts with a large all-sky sample of galaxy clusters as potential lenses. We find a total of 17 candidate lensed GRBs defined by a 2 arcminute search radius from a cluster in our sample. 14 of our candidates are either confirmed to be at higher redshifts than their cross-matched cluster, or are consistent with a higher redshift origin based on the Amati relation between Ep, i and Eiso of GRBs, indicating they are, at some level, lensed by their nearby cluster. Using the Amati relation and the lens-GRB separation, we quantify the magnification experienced by each GRB. We find μ 10 for all except for one candidate, GRB 071031, which is consistent with μ 10, but is uncertain. Another candidate, GRB 050509B, does not have a directly measured redshift, but was previously assumed to be at the redshift of its nearby cluster, z = 0. 225. We produce a lens model of this cluster and show that GRB 050509B is consistent with z 1 and magnified by μ ≃ 2 − 6. We present these findings in anticipation of future lensed GRB discoveries enabled by facilities such as the Vera C. Rubin Observatory in the coming years.
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