Williams, a 23-time Grand Slam singles winner, has played only three tournaments in the past 12 months and is ranked 183rd in the world.
Slovakia’s world number 32 Dominika Cibulkova has not been seeded.
On Tuesday, Cibulkova said it would not be fair for Williams to be seeded ahead of her.
“I don’t think it’s the right thing to do,” said the 29-year-old. “I think it’s just not fair. I have tried and I should be seeded. If they put her in front of me then I will lose my spot that I am supposed to have.”
Simona Halep is the top seed, with Roger Federer her counterpart in the men’s draw.
Federer is seeded a place higher than his world ranking, with world number one Rafael Nadal the second seed.
With the exception of Williams, all of the women are seeded in line with their WTA ranking.
Williams is seeded one place lower than Maria Sharapova, who she was due to meet in the fourth round of the French Open before pulling out because of injury. Her sister Venus is the ninth seed.
British number ones Johanna Konta and Kyle Edmund – the latter of whom is the world number 18 – are seeded 22nd in their respective draws.
Because of different rules in the two draws, Andy Murray cannot be seeded as he sits outside the top 32 in the rankings.
Britain’s three-time Grand Slam champion is returning from a hip injury.
How do the seedings work?
The Wimbledon seedings for the men are determined by the ATP ranking list of the top 32 players, but can be rearranged based on an individual’s grass-court record.
Ranking points are counted from competition in the two years running up to the tournament.
For the women’s game, the seeding order follows the WTA ranking list, but the All England Club reserves the right to make a change if it “is necessary to produce a balanced draw”. In 2017, no changes were made.
‘Decision will not be universally popular’ – analysis
Williams will not have to face another seeded player before the third round, but at that stage should expect to run into one of the top eight in the world. So the protection a seeding offers her will be limited.
Cibulkova’s view that the decision is unfair is shared – both privately and publicly – by very many WTA players, so the All England Club’s decision will not be universally popular.
But the committee clearly feel Williams is a unique case: an extraordinary champion who has only been able to play three events in the past year after giving birth to her first child in September.
As well as Nadal and Federer switching places at the top of the rankings, Marin Cilic moves up to number three and Novak Djokovic is up five to 12.
Milos Raonic is this week’s highest climber – up from 32 to 13.
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