Speculators in euro futures grew a net long position to its largest level since late February in the week ended May 25, data from the Commodity Futures Trading Commission showed on Friday.
The data from the CFTC's Commitments of Traders report on speculative positioning are used by analysts as an indicator of future market direction.
For example, extreme net long speculative positions often signal a decline in the currency, especially if that position conflicts with the positioning of the more influential commercial players.
Speculators generally are trend followers seeking to pick a precise top or bottom in the market.
The net long euro position increased to 18,714 contracts in the latest period, from last week's net long position of 13,422 contracts.
"What stands out is really a very clear surge in interest in the euro as the net long positions increased to the highest level ... since the time when the euro hit all-time highs three months ago," said Ashraf Laidi, chief currency analyst at MG Financial Group in New York.
The euro hit record highs around $1.2927 on Feb. 18.
The data "shows that the speculators have been instrumental in lending the euro the vital support ... and do not have that much faith in the US dollar," Laidi added.
June euro futures gained during the CFTC's reporting period to a close of $1.2099 on May 25 from a close of $1.2006 on May 19.