There is never a wrong time to invest in mutual funds for retirement. So, if you're still looking for the best mutual funds, the Zacks Mutual Fund Rank can be a great guide.

The easiest way to judge a mutual fund's quality over time is by analyzing its performance, diversification, and fees. Using the Zacks Mutual Fund 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.

Fidelity Advisor Mega Cap Stock M (FTGRX): 1.11% expense ratio and 0.6% management fee. FTGRX is classified as a Large Cap Blend fund. More often than not, Large Cap Blend mutual funds invest in companies with a market cap of over $10 billion. Buying stakes in bigger companies offer these funds more stability, and are well-suited for investors with a "buy and hold" mindset. FTGRX has achieved five-year annual returns of an astounding 15.7%.

Artisan Global Equity Investor (ARTHX Quick QuoteARTHX - Free Report) is a stand out amongst its peers. ARTHX is a Global - Equity mutual fund. These funds invest in large markets like the U.S., Europe, and Japan, and operate with very few geographical limitations With five-year annualized performance of 11.51%, expense ratio of 1.35% and management fee of 0.9%, this diversified fund is an attractive buy with a strong history of performance.

Transamerica Large Cap Value R6 (TALCX). Expense ratio: 0.63%. Management fee: 0.59%. Five year annual return: 12.57%. TALCX is a Large Cap Value mutual fund, which invests in stocks with a market cap of $10 billion of more, but whose share prices do not reflect their intrinsic value.

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.