If you're invested in any of the funds in our "Magnificent Retirement Mutual Funds" list, congratulations on owning some of the best managed and top-performing mutual funds. If you are lucky enough to discover our list of Top-Ranked Funds for the first time, it's never too late to start investing with the best, especially when it comes to your retirement.

The easiest way to judge a mutual fund's quality over time is by analyzing its performance, diversification, and fees. Using our Zacks Rank of over 19,000 mutual funds, we've identified three outstanding mutual funds that are ideally suited to help long-term investors pursue and achieve their retirement investing goals.

Let's take a look at some of the highest Zacks Ranked mutual funds with the lowest fees.

Oppenheimer Gold & Special Mineral Y (OGMYX Quick QuoteOGMYX - Free Report) : 0.92% expense ratio and 0.68% management fee. Sector - Precious Metal funds like OGMYX normally invest in stocks focused on the mining and production of precious metals such as gold, silver, platinum, and palladium. With annual returns of 11.5% over the last five years, this fund is a winner.

BlackRock Advantage Large Cap Growth I (CMVIX Quick QuoteCMVIX - Free Report) . Expense ratio: 0.62%. Management fee: 0.57%. CMVIX is a part of the Large Cap Growth mutual fund category, which invest in many large U.S. companies that are expected to grow much faster compared to other large-cap stocks. This fund has managed to produce a robust 12.49% over the last five years.

T. Rowe Price Mid-Cap Growth Fund (RPMGX Quick QuoteRPMGX - Free Report) . Expense ratio: 0.74%. Management fee: 0.61%. Five year annual return: 12.75%. RPMGX is a Mid Cap Growth mutual fund. These mutual funds choose companies with a stock market valuation between $2 billion and $10 billion.

We hope that your investment advisor (if you use one) has you invested in one or all of the top-ranked mutual funds we've reviewed. But if that isn't the case, it might be time to have a conversation or reconsider this vitally important relationship.

Do You Know the Top 9 Retirement Investing Mistakes?

Investing in underperforming mutual funds is just one of the key errors that can derail your retirement plans.

To learn more, read our just-released report: 9 Retirement Mistakes You Need to Avoid.