You have to be an adult to open an account. However, you can have an adult open an account for you, and that person will be legally and financially responsible for everything you do.
In the US you have to be 18. You’re only limited to how much you can spend. Be careful how many transactions you plan to do. You will be charged per transaction. Also you will be taxed heavily for any stocks sold.
You must be 18 to do it by yourself. Or you can much easier have a parent or guardian open an account and do it for you. Or you probally have an account setup underneath your parents like a joint account. And you might be able to join an investing club where a bunch of poeple meet up and talk about investments and all pool your money together and invest. Don’t think you’ll need an age there either.
Most brokers require you to be 18 to set up an account along with a minimum deposit of $2,000. My suggestion to you is to practice paper trading while saving money till your 18. Practice trading trends and getting used to market fluctuations that way when it comes time for the real thing you are aware of the risk and rewards.
A great place to paper trade is updown.com where you compete against other users and can win actual money.
Also if you are looking to learn more about the market email any questions you might have and I’d be glad to give you some help. I also keep a blog that you can visit at that I try to keep updated with recent news and my own investment advice. Readers can also leave their own comments and share their advice. I created the blog in hopes that readers of all investment experience could learn from one another and share advice and experiences.
Hope I have helped and Good Luck!