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Ballet loves a good anniversary and 2009 is a big one. It's the centenary of the founding of Serge Diaghilev's Ballets Russes, the most influential ballet company of the 20th century, and all kinds of people are jumping on the celebration bandwagon. And why not? The impact of Diaghilev's Russian artists was so enormous, his ideas so revolutionary, that we are still feeling the impact of his genius today. Nothing can match the excitement of the company's performances in Paris before the First World War, when Nijinsky, Karsavina, Stravinsky and Fokine made ballet the must-see entertainment of its day, but British dancers and choreographers are planning to honour the Ballets Russes in their own way.

The Royal Ballet will take a backward glance by reviving two iconic Fokine works, Les Sylphides (in a new staging by Monica Mason) and The Firebird (opens May 4), fine works both, though it strikes me as a fairly muted reaction to such an important milestone. English National Ballet, which boasts a direct lineage from the Ballets Russes, also revisits some of the troupe's greatest works in a Sadler's Wells season (June 16-20) that includes guests from the Australian Ballet. Highlights include Sylphides, Le Spectre de la Rose, Scheherazade and The Dying Swan, along with David Dawson's new reimagining of Nijinsky's L'après-midi d'un Faune.

New is the mantra at Sadler's Wells which is commissioning four works from contemporary choreographers - Russell Maliphant, Wayne McGregor, Javier De Frutos and Sidi Larbi Cherkaoui - that encapsulate the spirit of Diaghilev. They will be performed in the autumn of 2009.

It's also the year for second thoughts. David Bintley, who earlier rescued his failed Cyrano with a completely new production for Birmingham Royal Ballet, is planning to rework Sylvia for the same company. Gods and goddesses, slave girls and pirates, and all that lovely music by Delibes make this one of the most cherished comedies of the 19th century. After its Birmingham premiere (Feb 25) the production moves to the London Coliseum (April 16-18) as part of the Spring Dance season, which kicks off with American Ballet's Theatre's blockbuster Swan Lake (March 25-31).

Even more radically, Kenneth MacMillan's widow is devising a new one-act production of his rarely performed Isadora. His tribute to the great free spirit of Isadora Duncan started life as a full-length ballet in 1981 but was never a success, so Deborah MacMillan is determined to resurrect its rather dubious reputation at Covent Garden (it opens on March 11). She'll have her hands full on this one.

Two veteran ballerinas will feature largely in the year's news. Sylvie Guillem may have hung up her pointe shoes long ago, but she continues to fascinate audiences with her rebirth as a contemporary dancer. The next stop on her artistic adventure is the potentially fascinating Eonnagata, a collaboration with Maliphant and the Canadian theatre director Robert Lepage (see box).

Agnes Oaks, the English National Ballet star, takes her final bow in the spring tour of Manon after a farewell at Sadler's Wells (Jan 30). For 20 years Oaks has been one of the most luminous dancers in Britain and her partnership with her husband Thomas Edur has been unsurpassed on our stages. Elsewhere, a farewell of another sort, as the choreographer Tanja Liedtke, who died in Australia in 2007 at the age of 29, is showcased when her final production, Twelfth Floor, embarks on a large UK tour that starts in Warwick on February 10.

If you think that all sounds too much like a trip down memory lane, panic not. The choreographer William Forsythe, never one to rest on his laurels, is being celebrated in a wacky season that brings his provocative explorations to a number of London venues, including Tate Modern (April 30-May 1), where hundreds of pendulums will fill the cavernous Turbine Hall. The concept of dance is in there somewhere.

Must-see: Eonnagata

From Feb 26, Sadler’s Wells

The most exciting collaboration takes place at Sadler’s Wells in February when the ballerina Sylvie Guillem (left), theatre director Robert Lepage and choreographer Russell Maliphant unveil Eonnagata. It’s inspired by the life of one of Louis XV’s spies, Charles de Beaumont, who carried out his secret duties in the guise of a transvestite. He was so successful that people were never really sure of his true gender. Alexander McQueen designs the costumes. www.sadlerswells.com

Royal Opera House, London WC2: www.roh.org.uk; 020-7304 4000

Sadler's Wells, London EC1: www.sadlerswells.com; 0844 8710090

Birmingham Hippodrome: www.brb.org.uk; 0870 7301234

London Coliseum: www.eno.org; 0871 9110200

Twelfth Floor: www.twelfthfloortour.co.uk

Focus on Forsythe: www.sadlerswells.com/forsythe

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