<p>O'Neill agreed a one-year contract with the option of a further year's extension.</p><p>He spent two spells in temporary charge of Celtic during a chaotic campaign that ended in spectacular fashion.</p><p><strong>"It is once again a great privilege for me to continue as Celtic manager,"</strong> O'Neill said Thursday.</p><p><strong>"Last season will live long in all our memories and to be part of that success has in a big way whetted the appetite to work again for more days like those and bring our supporters those moments."</strong></p><p>O'Neill, who had already enjoyed a successful stint at the Glasgow club from 2000-2005, first returned to Celtic Park in October after Brendan Rodgers's exit.</p><p>Despite winning all eight of his domestic matches, O'Neill left when Wilfried Nancy was hired on a full-time basis.</p><p>However, Nancy was quickly axed following a miserable run and O'Neill returned in January.</p><p>O'Neill inspired a remarkable title-winning campaign as Celtic pipped Hearts on the final day of the season with a dramatic win against the Edinburgh club.</p><p>Hearts, chasing a first title since 1960, led the way for much of the season but Celtic benefitted from a hugely controversial penalty to beat Motherwell in their penultimate game.</p><p>O'Neill's men came back from a goal down to beat Hearts in Glasgow in a last-day showdown, securing the club's fifth successive title.</p><p>Seven days later, O'Neill secured his ninth trophy as Celtic manager when the Hoops beat Dunfermline 3-1 in the Scottish Cup final.</p><p>Former Celtic striker Robbie Keane had been linked with the job in recent weeks.</p><p>But pro-Palestinian Celtic fans opposed that potential move due to Keane's spell in charge of Israeli club Maccabi Tel Aviv.</p><p>Urging Celtic to build on last season's double, O'Neill said: <strong>"Celtic can never rest on past success so we are aiming to drive forward together as we aim to deliver again for the club and our fans.</strong></p><p><strong>"I thank our fans for their ongoing support, it means everything. I look forward to being back at Celtic Park, when we will come together and strive to bring our fans the success which that support deserves."</strong></p><p>Celtic's principal shareholder Dermot Desmond vowed the club will back O'Neill's vision in the transfer market.</p><p>The Celtic hierarchy has endured criticism from fans over their failure to spend big money on signings in the past.</p><p><strong>"Time and time again Martin has shown his qualities,"</strong> Desmond said.</p><p><strong>"We know he is a winner, we know what the club means to him and he continues to be the outstanding candidate.</strong></p><p><strong>"He knows the demands at Celtic and I know how determined he is again to bring success to the club and our supporters.</strong></p><p><strong>"The club will support Martin fully again across the close season to make sure we are well prepared to achieve domestic success and compete on the European stage."</strong></p>