In the women's draw, Halep is seeded 2nd after top-ranked Kerber
Three-time champion Novak Djokovic has been bumped up to second seed for next week's Wimbledon championship despite slipping to fourth in the ATP world rankings while seven-times champion Roger Federer has also benefited.
The seedings, released by the All England Club on Wednesday, have defending champion Andy Murray number one in the men's singles with Germany's Angelique Kerber the women's top seed.
Wimbledon differs from the other grand slams, in the men's singles at least, with previous form on grass in the previous two years coming into play to re-order the top 32 in the world rankings -- a system agreed by the ATP.
Spaniard Rafael Nadal, who won a 10th French Open last month, is second in the ATP rankings but will be seeded fourth at Wimbledon after a mediocre record there in recent years.
Despite winning the title twice, the 31-year-old has not been past the fourth round since 2011.
Favourite Federer, fifth on the ATP rankings, is seeded third which means he will avoid one of his biggest rivals for the title until the semi-finals.
Fellow Swiss Stan Wawrinka, runner-up at the French, drops to fifth seed, from his world ranking of three.
Other beneficiaries of the system include Luxembourg's grasscourt expert Gilles Muller who is seeded 16th compared to an ATP ranking of 26. Muller won the recent Den Bosch tournament and reached the semi-final at Queen's Club last week.
Queen's Club champion Feliciano Lopez, ranked 25, is seeded 19th.
The women's seeds stick strictly with the current WTA rankings. Romania's Simon Halep, who could take over the top spot this week if she wins the Eastbourne title, is seeded two.