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 best way to shortlist great mutual funds is to ensure solid performance, diversification, and low fees. Some are better than others, but utilizing the Zacks Mutual Fund Rank, we have identified three mutual funds that could be solid additions to one's retirement portfolio.

Let's take a look at some of our top-ranked mutual funds with the lowest fees.

If you are looking to diversify your portfolio, consider JPMorgan US Equity Fund R6 (JUEMX Quick QuoteJUEMX - Free Report) . JUEMX is part of the Large Cap Blend section, and these mutual funds most often invest in firms with a market capitalization of $10 billion or more. By investing in bigger companies, these funds offer more stability, and are often well-suited for investors with a "buy and hold" mindset. This fund is a winner, boasting an expense ratio of 0.44%, management fee of 0.4%, and a five-year annualized return track record of 11.09%.

William Blair Large Cap Growth N (LCGNX Quick QuoteLCGNX - Free Report) . Expense ratio: 0.9%. Management fee: 0.6%. LCGNX is a Large Cap Growth mutual fund, and these funds invest in many large U.S. firms that are projected to grow at a faster rate than their large-cap peers. This fund has managed to produce a robust 10.4% over the last five years.

Fidelity Select Health Care (FSPHX Quick QuoteFSPHX - Free Report) . Expense ratio: 0.68%. Management fee: 0.52%. Five year annual return: 9.82%. FSPHX is part of the Sector - Health category, offering investors a focus on the healthcare industry, one of the largest sectors in the American economy.

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.