Hannu Manninen was the worlds top Nordic combined athlete at the turn of 21st century and is considered the most decorated Finnish athlete in Nordic combined history. At the Olympic Winter Games, Manninen won a full set of medals, all in the team event – gold in 2002, silver in 1998 and bronze in 2006. His best individual finish at the Olympic Games was fourth in 2010 large hill. At the World Championships, Manninen won three titles, including his only individual medal at a major international tournament, gold in the 2007 sprint event, with his other titles coming in the 1999 and 2007 team event. Manninen also won team silver in 1997 and team bronzes in 2001 and 2003 at the World Championships.

During his career, Manninen won a record of 48 World Cup events and set a record with 89 podium finishes in World Cup races. He was the overall World Cup winner in four consecutive seasons from 2003-07, while finishing second in the 1998-99 season. He also won the Nordic combined event at Holmenkollen three times – in 2002, 2004, and 2005. During his career, Manninen also competed in cross-country events, mainly in sprint, including at the 2002 Winter Olympics, where he finished eighth.

Manninen finished his sporting career in 2011 and worked as a commercial airline pilot, serving as a co-pilot with Finnish airline Flybe Finland. His younger sister Pirjo Muranen (née Manninen) was a cross-country skier who won several World Championship medals, including three golds (sprint in 2001 and relay in 2007 and 2009). They were the first brother-sister combination to ever win gold medals at the same Nordic World Ski Championships (in 2007).