The pan-European Stoxx 600 closed up 0.20 percent, off its session highs, with sectors pointing in different directions by the close. The region was supported by a strong performance seen on Wall Street, as the first day of a new quarter kicked off.
The U.K.'s FTSE 100 ended slightly down, off 0.19 percent, while France's CAC 40 rose 0.24 percent and Germany's DAX jumped 0.75 percent. Markets in peripheral Europe showed a relatively mixed picture by the close.
In the corporate space, travel and leisure equities were some of the worst performers Monday following news that Ryanair had cut its full-year profit guidance. The stock sank 12.5 percent by the close, making it one of Europe's biggest losers. Other airlines were impacted by the news, with Easyjet down by 7 percent and Air-France-KLM dropping 4 percent.
In afternoon trade, Royal Mail shares tanked, after the postal service firm issued a statement on its performance. In the update, its group CEO Rico Back said that trading conditions in Britain were "challenging" and that its letter volumes had been impacted by business uncertainty, GDPR and ongoing structural decline. After the U.K. firm delivered its warning on profit and costs, shares sank some 18 percent.
German health firm Fresenius led Europe's gains, following a report that a Delaware judge ruled in its favor in a corporate dispute with Akorn. The judge's decision allows Fresenius to walk away from a $4.75 billion merger deal with the U.S. drugmaker. The stock surged 8.5 percent.
Linde was also one of the region's biggest gainers, closing up over 6 percent, after the group won regulatory approval from Chinese authorities to merge with Praxair.
Elsewhere, Danske Bank has appointed a new interim CEO. Jesper Nielsen, head of the Danish banking union, has replaced Thomas Borgen, who resigned last month after a money laundering investigation. Shares of the bank closed mildly higher.
President Donald Trump reached a deal with Canada and Mexico to replace the existing North American Free Trade Agreement (NAFTA), according to a senior U.S. administration official. The new deal has been named the USMCA — the United States-Mexico-Canada Agreement.
On Wall Street, stocks rallied on Monday, following the news that Canada had joined the U.S.-Mexico trade deal. The Dow Jones industrial average rose more than 200 points around Europe's close, while the and Nasdaq Composite also posted strong gains.
Back in Europe, U.K. Prime Minister Theresa May asked her party members to back her Brexit plan amid divisions over what the U.K.'s future relationship with the European Union (EU) should look like. During the party's annual conference, May's plans were criticized by two former ministers, including the former foreign secretary Boris Johnson.
In terms of data, the euro zone latest unemployment rate came in at 8.1 percent in August, its lowest level since November 2008.