Sports memorabilia has become increasingly popular and valuable in recent years, and is a market which continues to grow. While sporting mementos, keepsakes and autograph collecting have been fairly common place since the 1920s and 30s, memorabilia only really became serious business during the 1980s, coinciding with when sports teams first began selling jerseys/shirts. From this came the sale of used/signed shirts, and from that a real market for memorabilia and these kind of items opened up.

The most expensive pieces of memorabilia unsurprisingly tend to be from the most iconic athletes, teams and moments in sports history. This list only includes the price at which items have sold for, not that they are valued at. Items such as Joe DiMaggio's Journal and Geoff Hurst's 1966 World Cup final shirt have both been valued at well in excess of $1 million, but as neither have sold for or even near to those prices, they cannot rank on this list.

Similarly, a number of highly valuable items are kept in museums or were sold before the market for such items skyrocketed, and have not since become available. Remarkably, one man features seven times on this list, making up almost half of the entries. Items that narrowly missed out on the list include Shoeless Joe Jackson's Bat ($577,000) and Lou Gehrig's 1939 Yankees Uniform ($451,000). Here are the top 15 most expensive pieces of sports memorabilia:

15 15. Hank Aaron's 755th Home Run Ball - $650,000

Only Barry Bonds has hit more MLB home runs than Hank Aaron, the former Milwaukee/Atlanta Braves and Milwaukee Brewers right fielder. Aaron had an extraordinary career, and still holds the record for the most seasons as an All-Star (21) and the most All-Star Game Selections (25). The 1957 World Series champion hit the last of his 755 home runs in July 1976, at Milwaukee's County Stadium. The ball sold just over 20 years later for a fee of $650,000.

14 14. Babe Ruth's 1933 Jersey - $657,250

The man who ranks one place below Hank Aaron in terms of all-time home runs, but above all else in terms of iconic baseball players, Babe Ruth memorabilia is unsurprisingly highly sought after memorabilia. His 1933 season was one of a number of very impressive years for Ruth. The second to last year of his time with the Yankees, he batted .301, hitting 34 home runs, with 103 RBIs and a league-leading 114 walks. That year also saw Ruth's first All-Star selection and was the year in which he hit the first home run in All-Star Game history. His jersey from 1933 sold at auction for $657,250.

13 13. Babe Ruth's 1934 World Tour Uniform - $771,000

The fact that an athlete has worn an item almost always increases its value, and evidence of wear is often something a buyer will look out for. In this case, it was quite different. Babe Ruth's 1934 World Tour uniform had only been worn during an offseason tour to Japan, and the occasional exhibition game in later years. The fact it had been worn so little meant it was in quite excellent condition, and actually increased its value in comparison to a number of other Ruth jerseys. It was sold by Mastro Auctions in August 2005 for $771,000.

12 12. Babe Ruth Signed 1933 All-Star Game Home Run Ball - $805,000

As stated in entry number 14, Babe Ruth made history in 1933, when he became the first player in history to hit a home run in an All-Star Game. Whilst the jersey fetched $675,250, the ball faired even better, selling for a remarkable $805,000. The game, which was the inaugural All-Star Game, took place at Comiskey Park on July 6th 1933, in front of a crowd of 49,200. Ruth hit two home runs in the game. The combination of the history of the All-Star format, the celebrity of Babe Ruth and it being both the first All-Star Game and first home run unsurprisingly made this a highly valuable and collectible item.

11 11. Babe Ruth's 1932 Jersey - $940,000

The most observant readers out there may have caught on that it is Babe Ruth who is the man to feature seven times on this list, and it is that man again who comes in at number 11. The legendary slugger, best known for his home run power, became arguably the first great sporting celebrity during the Roaring Twenties and appears to be the most marketable athlete of all time when it comes to memorabilia.

This jersey is iconic because it was worn by Ruth for his iconic 'called shot'. When he stepped up to bat, with the scores tied at 4-4 against the Chicago Cubs in the 1932 World Series, Ruth pointed pointed to the bleachers in center field before hitting the ball exactly where he had pointed for his 15th home run of the year. The jersey sold for $940,000.

10 10. FA Cup - $956,000

The second most expensive piece of soccer memorabilia ever sold was the FA Cup in 1997. The Football Association Challenge Cup, better known today as simply the 'FA Cup', is the oldest football competition in the world and the most highly-regarded domestic knockout competition in English football. Founded in 1871, 736 teams are currently eligible to enter the competition, and Arsenal are the reigning champions, as well as holding the record for the most successes in the tournament, with 12 wins to their name.

Only four FA Cups have ever been made and only one sold. When sold for $956,000 in 2005, it overtook the Jules Rimmet World Cup as the most expensive piece of soccer memorabilia ever sold at that time. The trophy that was sold was the oldest of the four that had been made, and had been handed to the winner of the competition ever year between 1896 to 1910. It was bought by an unnamed telephone bidder.

9 9. Babe Ruth's 1919 Yankees Contract - $996,000

We come to Babe Ruth's fifth entry on the list. It is no surprise that this item is so valuable, given that it signaled a landmark moment and arguably one of the most important in baseball history. The sale of Babe Ruth by the Red Sox to the Yankees in 1919 was a shock to most in the sport at that time, but the fee of $100,000 proved to be a shrewd investment. Ruth hit 54 home runs in his first season with the Yankees in 1920, going on to become widely regarded as the greatest baseball player of all time. The item was sold privately for a fee of $996,000.

8 8. Muhammad Ali 1965 Floyd Patterson Fight Gloves - $1.1 million

Out of the hundreds of thousands and into the millions and, more surprisingly, someone who isn't Babe Ruth. Muhammad Ali is perhaps the most recognizable athlete of all time, and in many people's eyes the greatest; certainly in his own throughout the 1960s and 70s. Crowned both the 'Sportsman of the Century' by Sports Illustrated and 'Sports Personality of the Century' by the BBC, it will come as little shock to most the Ali memorabilia is highly lucrative.

More expensive than the gloves he wore in his first Sonny Liston fight, the gloves Ali wore when he beat Floyd Patterson in 1965 currently stand as the most expensive piece of Ali memorabilia ever sold, although if the gloves from either the 'Rumble in the Jungle', the 'Thrilla in Manilla' or Ali's first fight with Fraizer were to go on sale in today's market, one suspects they would exceed the $1.1 million spent on the Patterson fight gloves.

7 7. Sheffield Football Club Rules, Regulations & Laws -$1.24 million

Association football memorabilia is a market which has seen growth even greater and more rapid than most in recent years, but despite being by far the biggest sport on Earth, only two entries from the sport make this list. The 'Sheffield Football Club Rules, Regulations and Laws' are believed to be the first official rules for football ever drafted.

Put together by Sheffield FC, the oldest active football club in the world, in 1857, the year after they were founded, it was sold by the club for $1.24 million in 2011 to raise funds to an anonymous bidder at Sotheby's auction house. The book outlined rules that still stand today, such as the indirect free-kick, the corner kick and outlawing both hacking and tripping.

6 6. Babe Ruth 1923 First Yankee Stadium Home Run Bat - $1.265 million

Number six and it's that man again. The first and only bat to make this list, it is stated in the Guinness Book of World Records as the most expensive bat of all time. Quite rightly too in many respects. The bat was used by Ruth in the first ever game at the original Yankee Stadium, often referred to as 'The House That Ruth Built', such was his importance in kick-starting the Yankees fame and success.

The bat became more iconic still as Ruth not only hit the first Yankee Stadium home run, but also did so against his former team and rivals, the Boston Red Sox. The bat was sold at Sotheby's in New York in 2004 for a fee of $1.265 million.

5 5. Paul Henderson 1972 Jersey - $1.275  million

Perhaps the least well-known athlete globally on this list, Paul Henderson is a Canadian national hero, on a level attained by very few in any country, and it is not difficult to see just why his 1972 jersey became so valuable. Canada and the USSR were - quite rightly - regarded as the two finest ice hockey nations on Earth at that time, but as Canada had withdrawn from the IIHF, a 'Summit Series' was created in 1972, an eight-game series between the two nations to determine who was truly the best.

The Soviets led 3-1 at one stage, with one draw, but the Canadians won the last 3 contests to take a 4-3-1 win in the series. Henderson scored the winning goals in the sixth, seventh and eighth games, the last of which came 34 seconds from time, deciding the entire series in one of the most dramatic sporting climaxes in history. The Series was seen as not just a hockey battle but a cultural and ideological one, coming during the heart of the Cold War. Henderson has since been made a Member of the Order of Canada, and his legendary jersey sold for $1.275 million, far more than any other hockey jersey in history.

4 4. Honus Wagner 1909 Baseball Card - $2.8 million

Widely regarded as one of the greatest MLB players of all time, and certainly one of the finest of the sports earlier years, with only Ty Cobb as genuine competition, Honus Wagner played baseball for 21 years with the Louisville Colonels and the Pittsburgh Pirates. Nicknamed 'The Flying Dutchman', Wagner was one of the first five members of the Baseball Hall of Fame in 1936, receiving the second most votes, behind only his contemporary Cobb, and tied in second with Babe Ruth.

Wagner's card became so expensive as he refused the makers, the American Tobacco Company, to feature him, as he didn't want children buying cigarettes. This made the card increasingly rare, and a near-mint condition card sold in 2007 for $2.8 million.

3 3. Mark McGwire's 70th Home Run Ball - $3 million

Ten entries on this list are from the sport of baseball, and Mark McGwire's 70th home run ball is the ninth of these. An outstanding player, Mark McGwire set the record for the most single-season home runs in history with 70, smashing the previous record of 61, only to see his record be topped three years later by Barry Bonds. McGwire still holds the record for the highest at bats per home run ratio in history, with a record of a home run once every 10.61 at bats, the second highest is Babe Ruth with 11.76.

The 12 time All-Star and two-time World Series winner set a myriad of other records over the course of a 16-year career in which he turned out for Oakland Athletics and the St. Louis Cardinals. 'Big Mac', as he was often known, hit 583 home runs, but it was the 70th of the 70 he hit in 1998 that became the most iconic. The ball that McGwire made history with, hitting that 70th home run, sold for $3 million.

2 2. James Naismith's 1891 Rules of Basketball - $4.3 million

Canadian-born physical educator, physician and innovator James Naismith moved to the U.S. after studying in Montreal, and developed the modern sport of basketball while working as a teacher in 1891, writing the first rules of the sport that same year. A doctor of medicine, Naismith is considered the outright inventor of basketball, and his original rules of the sport remain intact today and currently stand as the second most expensive piece of sports memorabilia ever sold. The rules sold at auction for a price of $4,338,500.

1 1. Babe Ruth 1920 Jersey - $4.415 million

It simply had to be Babe Ruth who topped this list didn't it. The man who dominates the list constituting just shy of half the entries, Ruth also takes top spot, with the most expensive piece of sports memorabilia ever sold. The record was set when the item was sold at auction in 2012, eclipsing the fee paid for Naismith's rule book which had been set two years earlier. The item, described as 'the most desirable baseball artifact' in history, had previously been kept at the Babe Ruth Birthplace Museum.

The incredible price is said to be because the jersey is the oldest known New York Yankees jersey worn by Ruth. Its significance in the power-shift of baseball, as well as its cultural impact on New York outside the world of sport, is massive. The jersey which was first worn in 1920, sold for $4,415,658, and far exceeds even the second most expensive item of Babe Ruth memorabilia.