Sheldon's laptop is a laptop which is owned by Sheldon Lee Cooper. It is a red laptop, possibly a Dell laptop. Sheldon uses his laptop for work and sometimes to play games with Howard, Leonard and Raj. Sometimes, Sheldon's laptop is seen in the California Institute of Technology.
In the episode "The Bozeman Reaction", towards the start of the episode, his belongings, including his laptop were stolen and Sheldon called the police about it. While Sheldon eventually gets his belongings back, he has to get a new laptop to replace the stolen one.
In the episode "The Parking Spot Escalation", Howard is seen using Sheldon's laptop in Sheldon's spot, as revenge for Sheldon taking Howard's $500 limited edition Iron Man helmet. Sheldon later sells that laptop to a dry cleaner at the end of the episode - the laptop is then replaced by an identical model from the next episode onwards.
In "The Solder Excursion Diversion" Sheldon's three-and-a-half-year-old laptop dies and Amy buys him a new one. Even though Sheldon is skeptical, she knows him well enough to buy exactly what features he wanted in a computer.