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 learn about some of Zacks' highest ranked mutual funds with low fees you may want to consider.

MSIF Growth Portfolio L (MSHLX Quick QuoteMSHLX - Free Report) : 1.32% expense ratio and 0.4% management fee. MSHLX is a Large Cap Growth option; these mutual funds purchase stakes in numerous large U.S. companies that are expected to develop and grow at a faster rate than other large-cap stocks. MSHLX has achieved five-year annual returns of an astounding 23.03%.

T. Rowe Price Diversified Mid Cap Growth (PRDMX Quick QuotePRDMX - Free Report) is a stand out amongst its peers. PRDMX is a Mid Cap Growth mutual fund. These mutual funds choose companies with a stock market valuation between $2 billion and $10 billion. With five-year annualized performance of 12.08%, expense ratio of 0.8% and management fee of 0.64%, this diversified fund is an attractive buy with a strong history of performance.

Polen Global Growth Instl (PGIIX Quick QuotePGIIX - Free Report) : 1.1% expense ratio and 0.85% management fee. PGIIX is a Global - Equity mutual fund investing in bigger markets like the U.S., Europe, and Japan; these kinds of funds aren't limited by geography. With a five-year annual return of 14.89%, this fund is a well-diversified fund with a long track record of success.

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.