Reality star Kim Kardashian is engaged to her boyfriend of six months, basketball star Kris Humphries.

Kardashian, 30, told People magazine she was in "shock" when she entered her Beverly Hills home last week to discover Humphries on bended knee with "will you marry me" spelled out in rose petals.

Humphries, 26, gave Kardashian a 20.5-carat Lorraine Schwartz diamond ring, worth an estimated $US2 million ($1.9 million).

The couple began dating in November and plan to marry this year.

Kardashian also hopes to start a family within months of exchanging vows with the New Jersey Nets player.