A high roller, also referred to as a whale, is a gambler who wagers large amounts of money. High rollers often receive lavish "comps" from casinos to lure them onto the gambling floors, such as free private jet transfers, limousine use and use of the casinos' best suites. Casinos may also extend credit to a player to continue betting, offer rebates on betting turnover or losses, and salaries of employees may also contain incentive arrangements to bring in high rollers.
The definition of a high roller varies. At Crown Casino in Australia, for example, it involves bringing between A$50,000 and $75,000 to the table. High roller players often have very high table limits allowing the high roller exclusive use. Casinos compete on bet limits. In Australia limits of A$300,000 are common, in Las Vegas they are between US$150,000 and $300,000, and in Macau they are up to US$500,000. Only casinos with "substantial financial firepower" can accommodate high-stakes gambling due to the "volatility" of results.
High rollers may also be subject to exceptions from various rules and regulations; for example the high roller rooms at Crown Casino in Melbourne, Australia are the only licensed venue in the state not subject to a ban on smoking.
High rollers are said to provide only a small fraction of casino "action." John Eidsmoe, in his book Legalized Gambling: America's Bad Bet, claims that it is actually gamblers from the lower and lower-middle classes in the United States that provide much of the gambling money. "The occasional wealthy 'high roller' does indeed exist, but he is the exception, not the standard. The fact that more than 50% of Nevada's gambling income comes from slot machines as opposed to the card tables should be an indication high rollers are not the main source of revenue."
One example of a high roller is an Australian man who turned over more than A$1.5 billion in a 14-month period from 2005, becoming "one of Crown's largest Australian players but not in the same league as [its] top international players". There have been many cases around the world where high rollers have committed fraud to provide funds for gambling beyond their means, after becoming seduced by the lifestyle. This was the case with famed gambler Terrance Watanabe who reputedly lost over $220M in Las Vegas over a 5 year period, and was ultimately sued by Caesars Entertainment for failing to pay up on markers he took out during the binge totaling $14.75M. 
While high rollers may not provide a significant portion of the revenues in the casino industry as a whole, they can have a major effect on the net income of casinos that cater to them. There are significant costs associated with attracting the highest stakes gamblers, so if a casino takes this chance and the patron wins, its expenses can be extraordinarily large. But if the casino's investment pays off and the high roller loses, the casino's gain can far exceed its expenses for the high roller's visit.
- Richard C. Paddock (February 15, 2009). "Debt finally topples a Las Vegas high roller". Los Angeles Times. articles.latimes.com.
- Kate Hagan (June 4, 2009). "Crown defends high-roller enticements". The Age. theage.com.au.
- Michael Warner (June 5, 2009). "Court told of concealed gambling by Crown Casino". Herald Sun. www.news.com.au. Archived from the original on 2009-06-07.
- Muriel Reddy (October 5, 2003). "Betting $330,000 on the turn of a card - National - www.theage.com.au". The Age. www.theage.com.au.
- Michael Warner (May 16, 2009). "Second high-roller deal for Crown casino". Herald Sun. www.news.com.au. Retrieved November 1, 2012.
- Eidsmoe, John Legalized Gambling; America's Bad Bet, 1994
- Anson Cameron (June 7, 2009). "High-stakes gamblers and the luck delusion". The Age. theage.com.au.
- Chee Chee Leung (August 28, 2004). "Casino glamor seduced lonely man into $1m fraud". The Age. theage.com.au.
- Vegas Guy (May 15, 2015). "Casino whale stories and profiles of biggest high rollers". Vegas Guy. www.vegasguy.com. Retrieved April 22, 2016.