Men's 800m Freestyle
· The men's 800m freestyle has been part of the world championships curriculum since 2001 and has been contested eight times at the worlds. It is the only men's freestyle event which is not contested at the Olympic Games.
· This event was won by Sun Yang (CHN) at each of the last three world championships, in Shanghai 2011, Barcelona 2013 and Kazan 2015.
· China has won the last four world titles in this event. Zhang Lin (CHN) triumphed in Rome in 2009, before Sun took over for his hat-trick.
· Zhang's winning time of 7:32.12 in Rome in 2009 still ranks as the current world record in this event.
· The last non-Chinese winner of this event was Przemyslaw Stanczyk (POL) in Melbourne in 2007.
· The first three men's 800m freestyle races in this tournament were all won by Australians: by Ian Thorpe (AUS) in 2001 and by Grant Hackett (AUS) in 2003 and 2005.
· Sun is the only Asian man to win the same event three times at world championships.
· Only one male swimmer not representing the United States has won the same individual event four times at the world championships. Grant Hackett (AUS) is a four-time champion in the men's 1500m freestyle.
· Sun (G3-S0-B0), Hackett (G2-S1-B0) and Ryan Cochrane (CAN, G0-S1-B2) share the record for most medals (three) in this event.
· Gregorio Paltrinieri (AUS) took silver in 2015. He won gold in Rio in the men's 1500m event and he could now give Italy its first world championships gold in the men's 800m.
· Mack Horton (AUS) claimed bronze in 2015 in the men's 800m. Coming to the World Championships in Budapest he wanted to contest four freestyle events from 200m, 400m, 800m and 1500m. The only man to have won a medal in all four events at a single world championships is Grant Hackett, who achieved this in 2003 and in 2005.
Women’s 200m Freestyle
· Katie Ledecky (USA) is the reigning Olympic and world champion in the women's 200m freestyle.
· Ledecky has already won multiple world titles in the 400m, 800m and 1500m freestyle events. She can become the second swimmer, male or female, to win at least two world titles in four different individual events, after Michael Phelps (USA) who achieved this in five events.
· Ledecky can become the second woman to win multiple world titles in this event, after Federica Pellegrini (ITA) who won in 2009 and 2011.
· Pellegrini is also the last woman to win the 200m freestyle world title as the reigning Olympic champion, as she won the gold medal at the Beijing 2008 Olympic Games preceding her two world titles.
· Pellegrini won her 2009 world title in a world record time that still stands today (1:52.98).
· In addition, Pellegrini claimed three silver medals (2005, 2013, 2015) and one bronze medal (2007) in this event. Her six total medals are double the number by any other woman in this discipline (next, Yang Yu (CHN) with three).
· Pellegrini can become the first swimmer, male or female, to bag seven medals in an individual event at the world championships. She now shares the record of six with Ryan Lochte (USA, 200m individual medley).
· Pellegrini's six medals put Italy in joint-second place on the all-time medal table in this event, alongside East Germany (G1-S4-B1). Only United States have claimed more (11, G5-S3-B3).
· Pellegrini also claimed Olympic gold (2008) and silver (2004) in the 200m freestyle. Her eight medals combined in this event at the world championships and Olympic Games see her only trail the numbers of Phelps (9 in 100m and 200m butterfly) and Lochte (9 in 200m individual medley) in individual events.
· Sarah Sjöström (SWE), a silver medallist in this event at the Rio 2016 Olympic Games, is hoping to become the second Swedish to finish on the podium in the women's 200m freestyle at the world championships, after Josefin Lillhage who took the bronze medal in 2005.
· In 2013 and 2015 Sjöström took the silver medal in the 100m freestyle and in 2015 she claimed the bronze medal in the 50m freestyle. She can become the first woman to finish on the podium of the 50m, 100m and 200m freestyle events at the world championships.
· Matt Biondi (USA), Michael Klim (AUS) and Pieter van den Hoogenband (NED) bagged world championships medals in the 50m, 100m and 200m freestyle events on the men's side.
· Olympic bronze medallist in Rio Emma McKeon (AUS) is hoping to become the fifth Australian swimmer to claim a world championships medal in this event, after Kylie Palmer (silver in 2011), Giaan Rooney (gold in 2001), Julia Greville (bronze in 1998) and Hayley Lewis (gold in 1991).
Men's 50m Breaststroke
· The eight world titles in the men's 50m breaststroke have been divided among six swimmers, with only Oleg Lisogor (UKR, 2001 and 2007) and Cameron van der Burgh (RSA, 2009 and 2013) winning on multiple occasions.
· Cameron van der Burgh could become the first man to win three world titles in the 50m breaststroke - Yulia Efimova (RUS) could achieve this on the women's side.
· Van der Burgh has finished on the podium of this event at each of the last five world championships (G2-S1-B2) - the only male swimmer to reach the podium in an individual event at six consecutive world championships is Ryan Lochte (men's 200m individual medley, 2005-2015).
· In 2015 in Kazan, van der Burgh was beaten by Adam Peaty (GBR) - the Briton could now become the first to win successive world titles in the men's 50m breaststroke.
· In the semifinals on 4 August 2015, Peaty qualified in a new world record time of 26.42, beating the world record time of 26.62 set by van der Burgh in the heats earlier on the day.
· Coming into these world championships, the only swimmers representing Great Britain to have won multiple world titles in a single event are Liam Tancock (GBR, 2 in men's 50m backstroke) and David Wilkie (GBR, 2 in men's 200m breaststroke).
· Great Britain, Ukraine and South Africa have all won a joint-record two world titles in this event.
· Only South African swimmers (6) have claimed more world championships medals in this event than United States' swimmers (4), but they have failed to win a single world title (S2-B2).
· Felipe Lima (BRA) could become the second Brazilian swimmer to claim a medal in this event, after Felipe França (BRA, silver in 2009, gold in 2011).
Men's 200m Butterfly
· In 2015, László Cseh (HUN) won the world title in this event representing Hungary.
· For Cseh, the success came 10 years after winning his first world title, the men's 400m individual medley he won at age 19 in Montreal in 2005.
· In 2013 in Barcelona, this event was won by Chad Le Clos (RSA), who became the first swimmer from Africa to win this event at world championships.
· Before that, Michael Phelps (USA) won this event five times in a sequence of six world championships, with only Pawel Korzeniowski (POL) interrupting that winning run in 2005.
· Apart from Phelps and his five titles, Michael Gross (FRG) is the only other swimmer to have won this event more than once (in his case: twice) at the world championships.
· Michael Phelps has won five medals in this event at world championships. Next in line is Wu Peng (CHN) who has won four (G0-S1-B3), but never a gold.
· Chad Le Clos is the only swimmer who has finished on the podium at each of the last two world championships.
· Swimmers representing the United States have won 15 medals (G9-S3-B3) in this event, 11 more than any other nation in this event.