Yes if deposited before midnight 4/15.
BUT ask your IRA custodian if THEY will still accept and post 2018 contributions. Many financial institutions have rules that they take 2-4 days to post a contribution and will not accept a 2018 contribution at this late date.
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**