** Shares of data centre operator NEXTDC NXT.AX rise as much as 23.8% to A$17.39, set for their best day ever, if gains hold

** Stock hits its highest since October 22 and is among the top gainers on benchmark index .AXJO

** Co reports FY underlying EBITDA of A$216.7 million ($140.81 million), 1% ahead of Visible Alpha consensus estimate

** Expects FY26 net revenue in the range of A$390 million to A$400 million, higher than A$350.2 million posted in FY25

** Also expects FY26 underlying EBITDA between A$230 million and A$240 million, with the midpoint of the range in line with consensus estimates

** Citi analysts see potential upgrades of more than 10% to consensus FY27 EBITDA estimates following the results

** Stock up ~15% YTD, including day's move

($1 = 1.5389 Australian dollars)

(Reporting by Himanshi Akhand in Bengaluru)

((Himanshi.Akhand@thomsonreuters.com))