Can I sponsor my sister? How long will the process take?

The process is going to take about 10-12 years.

Assuming that you are a U.S. citizen (not just a permanent resident), and assuming that you want to sponsor your sister to become a permanent resident of the U.S. (not simply come to visit), you can file an immigrant petition for her (Form I-130). The wait time in F4 category (brothers and sisters of U.S. citizens) now is 12 years; natives of Mexico have to wait 16.5 years, natives of Philippines - 24 years (due to the fact that number of petitions filed for natives of these countries is much greater than the number of petitions for natives of all other countries).

As a US citizen, you can sponsor your sister for green card to come to the United States. To do this, you will file a Form I-130 petition for alien relative with CIS. The petition is under Family Fourth Preference category [sibling of US citizen] and it takes about 12 years to be approved. For example, the petitions in that category which are now current were filed on or before Apr. 2001. [It is longer for citizens of Mexico and Philippines] and most people, thinking about the long wait do not even bother to file. which is a huge mistake. So, the earlier you file, the lesser time you'd have to wait. While the process is admittedly very long, note that when it is eventually approved, if married, your sister at that time, may bring her husband and children to this country. Also, note that this is not the only option for your sister to come to the US and she may in fact be eligible for other types of visas which take considerably shorter time to approve. You should consult with an attorney to advise you about all the other alternatives that may be availing to you under current immigration law.

If you are a US citizen you may file an immigrant visa petition on her behalf, but it will be years for an available priority date.

If you are a US citizen, you can file an I-130 visa petition for her, but it could be 12 years or more before she can apply for an immigrant visa.

You can sponsor your sister if you are a US citizen. The time it takes to process depends on where she is from. Siblings are the in the 4th preference category, which is the lowest, so it will often take several years. It is recommended to file anyway.